Protocol for communicating data block copies in an error recovery environment

[0001] The present application claims the benefit and priority of U.S. provisional patent application Ser. No. 60/605,168 filed on Aug. 30, 2004 and entitled “Image Manipulation of Data,” which is herein incorporated by reference.

[0002] The present application is related to co-pending U.S. application Ser. No. 11/166,690, entitled “Systems and Methods for Organizing and Mapping Data,” filed on Jun. 23, 2005, co-pending U.S. application Ser. No. 11/215,958, “Systems and Methods for Event Driven Recovery Management”, filed on Aug. 30, 2005, co-pending U.S. application Ser. No. 11/216,874, entitled “Systems and Methods for Rapid Presentation of Historical Views of Stored Data”, filed on Aug. 30, 2005, and co-pending U.S. application co-pending U.S. application Ser. No. 11/215,930, entitled “Systems and Methods of Optimizing Restoration of Stored Data”, filed Aug. 30, 2005, which are herein incorporated by reference.

[0003] 1. Field of the Invention

[0004] The present invention relates generally to data recovery, and more particularly to a protocol for communicating data block copies in an error recovery environment.

[0005] 2. Description of Related Art

[0006] Conventionally, recovery management has been overseen by various systems that keep track of data being written to a storage medium. Recovery management may be necessary to recover data that has been altered by a disk crash, a virus, erroneous deletions, overwrites, and so on. Numerous other reasons are cited by companies and individuals for requiring access to data as it existed at one point in time.

[0007] Prior to recovery, data must be safeguarded by one or more back-up methods. Back-up methods may include copying files or databases so that they will be preserved in case of equipment failure or other catastrophe. Some processes may involve copying back-up files from a back-up media to a hard disk in order to return data to its original condition. Other techniques may include periodically copying the contents of all or a designated portion of data from the data's usual storage device to another storage medium so the data will not be lost in the event of a hard disk crash.

[0008] Back-up procedures, such as those described above, require a great deal of processing power from a server performing the back-ups of the data. For this reason, back-up procedures may be offloaded from a server so that the time ordinarily devoted to back-up functions can be used to carry out other server tasks.

[0009] For example, in some environments, an intelligent agent functions on a client device rather than the server in order to offload the back-up procedures. The intelligent agent may take a “snapshot” of a computer's data at a specific time so that if future changes cause a problem, the system and data may be restored to the way they were at the time of the “snapshot.”

[0010] Once copies of the data have been made in some manner, recovery management may be employed to recover the copies of the data. A data recovery system is designed to return the data to a state where it existed before certain changes were made to the data. The data may be recovered to different points in time, depending upon the state of the data a user wants to access.

[0011] Data recovery methods often require a user to know to what point in time the data is to be recovered. A tape, disk, or other back up medium can then be searched in order to recover the data as it existed at that particular point in time. Unfortunately, the user may not comprehend the best point in time to which to recover the data.

[0012] The present invention provides an exemplary system and method for storing information for later recovery. One or more first memory addresses within a recovery storage are assigned to one or more data blocks. One or more second memory addresses within a primary storage associated with the one or more data blocks and the one or more first memory addresses are sent to the recovery server. The one or more data blocks are copied to the one or more first memory addresses within the recovery storage.

[0023] FIG. 1 is a schematic diagram of an environment for organizing and mapping data in accordance with exemplary embodiments. Fibre Channel (FC) may be utilized to transmit data between the components shown in FIG. 1. However, any type of system (e.g., optical system), in conjunction with FC or alone, may be utilized for transmitting the data between the components.

[0024] The exemplary environment 100 comprises a production host 102 for creating various types of data. For example, a financial software program running on the production host 102 can generate checkbook balancing data. Any type of data may be generated by the production host 102. Further, the production host 102 may include any type of computing device, such as a desktop computer, a laptop, a server, a personal digital assistant (PDA), and a cellular telephone. In a further embodiment, a plurality of production hosts 102 may be provided.

[0025] The production host 102 may include a data interceptor 104. For example, a data tap that captures and duplicates data blocks or any other type of data may comprise the data interceptor 104 according to some embodiments. The data interceptor 104 may be any hardware, software, or firmware that resides on the production host 102, or otherwise accesses the data generated by the production host 102. For example, the data interceptor 104 may be embedded in a SAN switch or a disk array controller. According to exemplary embodiments, the data interceptor 104 may be coupled to, or reside on, one or more production hosts 102. Conversely, in some embodiments, the production host 102 may include or be coupled to more than one data interceptor 104.

[0026] The data interceptor 104 copies data created by the production host 102 and stores the data (“data blocks”) in a primary storage 106 associated with the production host 102. The copies of the data blocks (“data block copies”) are stored to recovery storage 108. The recovery storage 108 may comprise any type of storage, such as time addressable block storage (“TABS”). Although “data blocks” and “data block copies” is utilized to describe the data created and the copies of the data generated, files, file segments, data strings and any other data may be created and copies generated according to various embodiments. Further, the data blocks and the data block copies may be a fixed size or varying sizes. Further, the recovery storage 108 may comprise one or more recovery storage mediums. A recovery storage medium comprises any kind of storage, including but not limited to hard drives, RAM, firmware, and disks.

[0027] The primary storage 106 and/or the recovery storage 108 may include random access memory (RAM), hard drive memory, a combination of static and dynamic memories, or any other memory resident on the production host 102 or coupled to the production host 102. The primary storage 106 may include any storage medium coupled to the production host 102 or residing on the production host 102. In one embodiment, the data interceptor 104 may store the data blocks to more than one of the primary storage 106.

[0028] According to one embodiment, the data interceptor 104 can create data block copies from the data blocks after the production host 102 stores the data blocks to the primary storage 106 or as the data blocks are generated by the production host 102.

[0029] Data blocks are typically created from the production host 102 each instant a change to existing data at the primary storage 106 is made. Accordingly, a data block copy may be generated each time the data block is generated, according to exemplary embodiments. In another embodiment, the data block copy may comprise more than one data block. Each data block copy and/or data block may reflect a change in the overall data comprised of the various data blocks in the primary storage 106.

[0030] In exemplary embodiments, the data interceptor 104 intercepts each of the data blocks generated by the production host 102 in order to create the data block copies. The data block is sent to the primary storage 106 by the data interceptor 104, while the data interceptor 104 sends the data block copy to the recovery storage 108, as discussed herein. The data block copies may be combined to present a view of data at a recovery point (i.e., as the data existed at a point in time), called a “historical view.” In other words, the data block copies may be utilized to re-create the data (i.e., the data blocks stored in the primary storage 106) as it existed at a particular point in time. The “historical view” of the data may be provided to a user requesting the data as a “snapshot” of the data. The snapshot may comprise an image of the data block copies utilized to create the historical view, according to one embodiment.

[0031] In an alternative embodiment, the data interceptor 104, or any other device, may compare the data blocks being generated with the data blocks already stored in the primary storage 106 to determine whether changes have occurred. The copies of the data blocks may then be generated when changes are detected.

[0032] The historical view may also be used to present an image of all of the data in the primary storage 106 utilizing some of the data block copies in the recovery storage 108 and some of the data blocks in the primary storage 106. In other words, the historical view at time x may be recreated utilizing some of the data blocks from the primary storage 106 and some of the data block copies from the recovery storage 108, rather than only the data block copies from the recovery storage 108. Thus, the data block copies from the recovery storage 108 may be combined with the data blocks from the primary storage 106 in order to create the historical view.

[0033] In one embodiment, the production host 102 reserves private storage or temporary storage space for the data interceptor 104. The private storage space may be utilized by the data interceptor 104 for recording notes related to the data blocks, for temporarily storing the data block copies, or for any other purpose. For instance, if the recovery server 112 is not available to instruct the data interceptor 104 where to store the data block copies in the recovery storage 108, the temporary storage may be utilized to store the data block copies until the recovery server 112 is available.

[0034] Similarly, the temporary storage may be utilized to store the data block copies if the recovery storage 108 is unavailable. Once the recovery server 112 and/or the recovery storage 108 is once again available, the data block copies may then be moved from the temporary storage to the recovery storage 108 or any other storage.

[0035] In another embodiment, the data interceptor 104, using a bit map or any other method, tracks the data blocks from the production host 102 that change. Accordingly, if the recovery server 112 and/or the recovery storage 108 is unavailable, the data interceptor 104 records which data blocks on the primary storage 106 change. The data interceptor 104 can copy only the data blocks from the primary storage 106 to the recovery storage 108 that changed while the recovery server 112 and/or the recovery storage 108 were unavailable. Specifically, the data interceptor 104 or any other device flags each data block generated by the production host 102 that changes. The flags are referenced when the recovery server 112 and/or the recovery storage 108 are available to determine which data blocks were changed during the time the recovery server 112 and/or the recovery storage 108 were unavailable. Although each data block may change more than one time, each of the data blocks reflecting the most recent change to the data blocks when the recovery server 112 and/or the recovery storage 108 become available are the data blocks that are copied to the recovery storage 108 from the primary storage 106.

[0036] In yet another embodiment, the data interceptor 104 may continue to store the data block copies to an area of the recovery storage 108 allocated for data block copies from the data interceptor 104 by the recovery server 112 prior to the recovery server 112 becoming unavailable. In other words, if the recovery server 112 is unavailable, but the recovery server 112 has previously instructed the data interceptor 104 to store the data block copies to a specified area of the recovery storage 108, the data interceptor 104 can continue to store the data block copies to the specified area until the specified area is full and/or the recovery server 112 becomes available.

[0037] In still a further embodiment, a backup recovery server may be provided to provide the recovery server 112 functions if the recovery server 112 is unavailable. As discussed herein, more than one recovery server 112 may be provided. Similarly, more than one production host 102 may be provided, as a set of computing devices or other configuration, with other production hosts 102 in the set capable of performing functions associated with the production host 102 in the event the production host 102 becomes unavailable. The process of restoring data is described in further detail in co-pending U.S. application Ser. No. 11/215,930, entitled “Systems and Methods of Optimizing Restoration of Stored Data,” filed on Aug. 30, 2005.

[0038] The exemplary data interceptor 104 also creates metadata in one or more “envelopes” to describe the data block copies and/or the data blocks. The envelopes may include any type of metadata. In exemplary embodiments, the envelopes include metadata describing the location of the data block in the primary storage 106 (i.e., a logical block address “LBA”), the size of the data block and/or the data block copies, the location of the data block copy in the recovery storage 108, or any other information related to the data. In exemplary embodiments, the envelopes associated with the data block copies preserve the order in which the data blocks are created by including information about the order of data block creation by the production host 102.

[0039] The data interceptor 104 forwards the envelopes to a recovery server 112. The data interceptor 104 may associate one or more unique identifiers, such as a snapshot identifier (“SSID”), with the data block copies to include with one or more of the envelopes. Alternatively, any device can associate the unique identifiers with the one or more envelopes, including the data interceptor 104. The recovery server 112 may also designate areas of the recovery storage 108 for storing one or more of the data block copies in the recovery storage 108 associated with the one or more envelopes. When the data interceptor 104 stores the data block copies to the recovery storage 108, the data interceptor 104 can specify in the associated envelopes where the data block copy was stored in the recovery storage 108. Alternatively, any device can designate the physical address for storing the data block copies in the recovery storage 108.

[0040] The unique identifiers may be assigned to single data block copies or to a grouping of data block copies. For example, the recovery server 112 or other device can assign the identifier to each data block copy after the data block copy is created by the data interceptor 104, or the unique identifier may be assigned to a group of the data block copies.

[0041] The recovery server 112 uses the envelopes to create a recovery index (discussed infra in association with FIG. 3). The recovery server 112 then copies the recovery index to the recovery storage 108 as an index 110. The index 110 maps the envelopes to the data block copies in the recovery storage 108. Specifically, the index 110 maps unique identifiers, such as addresses or sequence numbers, to the data block copies using the information included in the envelopes. In alternative embodiments, the index 110 may be stored in other storage mediums or memory devices coupled to the recovery storage 108 or any other device.

[0042] In exemplary embodiments, the data interceptor 104 forwards the data block copies and the envelope(s) to the recovery storage 108. The recovery storage 108 may include the index 110, or the index 110 may otherwise be coupled to the recovery storage 108. More than one recovery storage 108 and/or indexes 110 may be utilized to store the data block copies and the envelope(s) for one or more production hosts 102 according to various embodiments. Further, the recovery storage 108 may comprise random access memory (RAM), hard drive memory, a combination of static and dynamic memories, direct access storage devices (DASD), or any other memory. The recovery storage 108 and/or the index 110 may comprise storage area network (SAN)-attached storage, a network-attached storage (NAS) system, or any other system or network.

[0043] The unique identifiers, discussed herein, may be utilized to locate each of the data block copies in the recovery storage 108 from the index 110. As discussed herein, the index 110 maps the envelopes to the data block copies according to the information included in the envelopes, such as the unique identifier, the physical address of the data block copies in the recovery storage 108, and/or the LBA of the data blocks in the primary storage 106 that correspond to the data block copies in the recovery storage 108. Accordingly, the recovery server 112 can utilize a sort function in coordination with the unique identifier, such as a physical address sort function, an LBA sort function, or any other sort function to locate the data block copies in the recovery storage 108 from the map provided in the index 110.

[0044] The recovery server 112 is also coupled to the recovery storage 108 and the index 110. In an alternative embodiment, the recovery server 112 may instruct the data interceptor 104 on how to create the index 110 utilizing the envelopes. The recovery server 112 may communicate any other instructions to the data interceptor 104 related to the data blocks, the data block copies, the envelope(s), or any other matters. Further, the recovery server 112 may be coupled to more than one recovery storage 108 and/or indexes 110.

[0045] As discussed herein, the index 110 may be utilized to locate the data block copies in the recovery storage 108 and/or the data blocks in the primary storage 106. Any type of information may be included in the envelope(s), such as a timestamp, a logical unit number (LUN), a logical block address (LBA), access and use of data being written for the data block, a storage media, an event marker associated with the data block, a sequence number associated with the data block, an identifier for a group of data block copies stemming from a historical view of the data, and so on.

[0046] In one embodiment, the envelopes are indexed according to the metadata in the envelopes, which may be utilized as keys. For example, a logical address index may map logical addresses found on the primary storage 106 to the data block copies in the recovery storage 108. A physical address index may map each physical data block copy address in the recovery storage 108 to the logical address of the data block on the primary storage 106. Additional indexing based on other payload information in the envelopes, such as snapshot identifiers, sequence numbers, and so on are also within the scope of various embodiments. One or more indexes 110 may be provided for mapping and organizing the data block copies.

[0047] One or more alternate hosts 114 may access the recovery server 112. In exemplary embodiments, the alternate hosts 114 may request data as it existed at a specific point in time or the recovery point (i.e. the historical view of the data) on the primary storage 106. In other words, the alternate host 114 may request, from the recovery server 112, data block copies that reveal the state of the data as it existed at the recovery point (i.e., prior to changes or overwrites to the data by further data blocks and data block copies subsequent to the recovery point). The recovery server 112 can provide the historical view of the data as one or more snapshots to the alternate hosts 114, as discussed herein.

[0048] The alternate hosts 114, or any other device requesting and receiving restored data, can utilize the historical view to generate new data. The new data can be saved and stored to the recovery storage 108 and/or referenced in the index 110. The new data may be designated by users at the alternate hosts 114 as data that should be saved to the recovery storage 108 for access by other users. The recovery server 112 may create envelopes to associate with the new data and store the envelopes in the index 110 in order to organize and map the new data in relation to the other data block copies already referenced in the index 110. Accordingly, the alternate hosts 114 or other device can create various new data utilizing the historical views as the basis for the various new data.

[0049] Each of the alternate hosts 114 may include one or more data interceptors 104 according to alternate embodiments. In another embodiment, a single data interceptor 104 may be coupled to one or more of the alternate hosts 114. In yet a further embodiment, the data interceptor 104 functions may be provided by the recovery server 112.

[0050] An interface may be provided for receiving requests from the alternate host 114. For instance, a user at the alternate host 114 may select a recovery point for the data from a drop down menu, a text box, and so forth. In one embodiment, the recovery server 112 recommends data at a point in time that the recovery server 112 determines is ideal given parameters entered by a user at the alternate host 114. However, any server or other device may recommend recovery points to the alternate host 114 or any other device. Predetermined parameters may also be utilized for requesting recovered data and/or suggesting optimized recovery points. Any type of variables may be considered by the recovery server 112 in providing a recommendation to the alternate host 114 related to data recovery.

[0051] The production host 102 may produce event marker to associate with the data blocks and/or the data block copies. For example, the data interceptor 104 may associate an end of a third quarter with data block copies indicating that the data block copies occurred during or around the end of the third quarter. In one embodiment, a request for a historical view constitutes an event and the event marker may be associated with the one or more data block copies comprising the historical view for later reference. For example, the historical view may be retrieved at a future time by referring to the event marker that indicates the last time the same historical view was requested.

[0052] The event markers may be associated with a clock associated with the primary storage 106, the recovery storage 108, or any other storage medium. Accordingly, the clock may assign a time to the storage medium as each copy of the data blocks are stored or in between storage of the data blocks.

[0053] Alternatively, the production host 102, the data interceptor 104, the recovery server 112, or any other device may assign one or more points in time to the copies of the data blocks themselves or the one or more points in time may comprise an event marker that identifies events that occur when the data block copies are not being stored to the storage medium. As discussed herein, event markers may comprise one or more points in time that do not coincide with the generation and/or storage of the one or more data block copies. In other words, the event markers may be associated with one or more points in time between the generation and/or storage of the one or more data block copies.

[0054] Thus, the event makers may simply indicate a state of the data in the primary storage 106 at the time a particular event associated with the event marker occurred. In other words, no data blocks may have been written and/or stored to the primary storage 106 when the particular event occurred.

[0055] In another embodiment, the events may be imported or provided by an entity or resource other than the production host 102 to associate with the event markers. Any source may provide events to associate with the event markers for the data blocks and/or the data block copies. The association of the event markers with the data blocks and/or the data block copies may be implicit or indirect. In other words, the event marker may be associated with a state of the data at a point in time, as discussed herein. A branching data structure and searching may be utilized to establish an actual state of the data corresponding with the point in time. For instance, a major news event may be associated with the data block copies for simple reference back to a noteworthy date, time, and so forth. The event markers may be associated with the data block copies as the data block copies are created by the data interceptor 104 or at any time after the data block copies have been created. Any type of event marker may be associated with the data.

[0056] A sequence number of each of the data block copies may be associated with the event marker. Accordingly, one or more data block copies associated with an event marker may be located according to the sequence number.

[0057] A text string may be provided for describing an event for the event marker. As discussed herein, any type of information may constitute an event. For example, a text string with an author's name may be included so that the data block copies may later be retrieved by searching for historical views comprised of data block copies associated with the author's name. In one embodiment, the author's name, or other text string, may be associated with an event marker, which is then associated with the data block copies. Accordingly, the author's name may not be directly associated with the data block copies. Similarly, a sequence number or any other unique identifier, as discussed herein, may be associated with the data block copy having the particular event marker associated with the data block copy. The unique identifier may then be utilized to locate the data block copy in the recovery storage 108 via the index 110. The data block copies required to reconstruct a historical view of data requested by a user may then be provided to the user, based on one or more events described by the user.

[0058] In exemplary embodiments, one or more event marker are utilized in combination with one or more timestamps in order to locate historical views that correlate with the one or more event markers. For example, if corruption to data occurred approximately ten minutes preceding a particular event from an event marker, or at any other time related to the event, the data can be recovered using the event and the data as it existed 10 minutes prior to the event. Any type of integration, combination, cross-reference, relationship, and so forth between the event markers and the timestamps or any other information may be utilized to locate or recreate the data. In another embodiment, a user can request all the data that occurred between one or more event markers.

[0059] The user may select an event or enter an event associated with the historical view desired in order to help the recovery server 112 locate the appropriate data block copies corresponding to the event marker in the recovery storage 108. The recovery server 112 can match the event information from the user with the event marker associated with the historical view. The event information from the user may directly match the event marker associated with the historical view or the recovery server 112 may determine what event marker best matches the event information from the user.

[0060] In some embodiments, the event information from the user can be matched with data outside of the recovery server 112. For example, a computing device that coordinates the activities of more than one recovery server 112 may receive the event information from the user and provide instructions to the recovery servers 112 for locating the event markers indicating the historical views that correlate with the event information or forward the request from the user to the recovery servers 112 or an appropriate recovery server 112.

[0061] Turning now to FIG. 2, an exemplary schematic diagram for data interceptor coordination of data block copies is shown. The data interceptor 104 may interact, for example, with the primary storage 106, the recovery storage 108, and/or the recovery server 112. The data interceptor 104 includes an intercept driver 202 in communication with a logging driver 204, which is in communication with a communications interface 206. A source initiating creation of the event markers may communicate with the data interceptor 104 in order to note the event markers in the envelopes. In some embodiments, the event markers may be created without coordination with the data interceptor 104.

[0062] The intercept driver 202 intercepts the data being generated by the production host 102. The intercept driver 202 then creates a data block from the data generated and a copy of the data block. In other words, the intercept driver 202 captures a data block copy each time a data block is created by the production host 102. The intercept driver 202 stores the data block to the primary storage 106 and forwards the data block copy to the logging driver 204. The data block copies may be generated every time a change to the data already stored in the primary storage 106 occurs.

[0063] The logging driver 204, which is coupled to, or otherwise in communication with, the intercept driver 202, generates the one or more envelopes with the metadata discussed herein. As also discussed herein, the metadata may include any type of information associated with the data blocks, such as a time generated, the sequence number, the location of the data blocks in the primary storage 106 and/or the data block copies in the recovery storage 108, the unique identifiers, the one or more event markers associated with the data block copies, and so on.

[0064] The logging driver 204 stores the data block copies to the recovery storage 108 along with the metadata. The logging driver 204 also sends the metadata to the recovery server 112 via the communications interface 206. The metadata sent to the recovery server 112 may be identical to the metadata stored to the recovery storage 108 or different. The recovery storage 108 is utilized for storage of the data block copies according to instructions from the recovery server 112 regarding where in the recovery storage 108 to store the data block copies, as discussed herein. Further, the envelopes are also stored in the recovery storage 108. As discussed herein, in an alternative embodiment, the data interceptor 104 may copy the data blocks from the primary storage 106 after the data interceptor 104 or the production host 102 stores the data blocks to the primary storage 106.

[0065] In one embodiment, the primary storage 106 and the recovery storage 108 may comprise one storage medium. For example, the recovery storage 108 may be utilized for storing the data blocks using a map of the data blocks, such as the branching data structure used by the recovery server 112. The map may be updated to reflect new data blocks being stored to the recovery storage 108 in such an embodiment.

[0066] In this embodiment, the production host 102 may be coupled to the recovery server 108, which in turn is coupled to a storage medium, such as the recovery storage 108. The recovery server 112 may include rules for implementing the branching data structure and a structure for the index 110. The recovery server 112 may use the index 110 and the LBA to determine the physical location of the data blocks in the recovery storage 108. The data block may then be provided to the production host 102 in response to any request(s) from the production host 102, such as a request for a historical view. When the production host 102 generates a data block and specifies an LBA, the recovery server 112 can allocate a free physical block in the recovery storage 108 for the data block. The recovery server 112 then updates the index 110 to map the LBA to the allocated free physical block and stores the data block generated into the allocated free physical block in the recovery storage 108.

[0067] Further, a data interceptor 104 may not be provided in accordance with such an embodiment. Instead, the recovery server 112 may perform the data interceptor 104 functions in this embodiment. The recovery server 112 may provide a historical view and store data blocks generated from the production host 102 utilizing the historical view, as discussed herein.

[0068] A communications interface 206 is coupled to, or is otherwise in communication with, the logging driver 204 and/or the recovery server 112. The communications interface 206 forwards the instructions from the recovery server 112, discussed herein, to the logging driver 204 indicating where the data block copies and/or the envelopes should be stored in the recovery storage 108. The recovery server 112 uses the envelopes to construct and maintain a recovery index within the recovery server 112 (discussed in association with FIG. 4). The recovery index is then copied as the index 110 in the recovery storage 108.

[0069] Specifically, the recovery server 112 sends configuration data to the logging driver 204 via the communications interface 206. The configuration data may include information regarding the area of the recovery storage 108 where the logging driver 204 may store the data block copies, or any other type of information. Any type of configuration data may be communicated to the logging driver 204 for storing the data block copies and/or the envelopes in the recovery storage 108 and/or for organizing the information from the envelopes in the index 110.

[0070] Although the data interceptor 104 is described as including various components, the data interceptor 104 may include more components or fewer components than those listed and still fall within the scope of various embodiments.

[0071] FIG. 3 illustrates an exemplary schematic diagram for management and storage communications in accordance with one embodiment. The exemplary production host 102 includes a management client 302, as well as the data interceptor 104 discussed herein. The exemplary recovery server 112 includes a management server 304 and an engine 306. Further, the alternate host 114 also includes a management client 308. As discussed herein, in some embodiments, the one or more alternate hosts 114 may also include data interceptors 104 for copying the data blocks generated while utilizing historical views of the data.

[0072] The management server 304 may be remotely connected to the recovery server 112 according to various embodiments. For example, if a plurality of recovery servers 112 are provided, each of the recovery servers 112 may be coupled to each of a plurality of management servers 304, for a one to one relationship. Alternatively, two or more recovery servers 112 of a plurality of recovery servers 112 may share one management server 304 amongst a plurality of management servers 304. Any number of recovery servers 112 may be coupled to any number of management servers 304 according to exemplary embodiments.

[0073] In further embodiments, each recovery server 112 may include a management server 304 that further communicates with the management clients 308. The management clients 308 may be coupled to any device, such as protected servers, alternate hosts 114, and so forth.

[0074] In one embodiment, the management server 304 is coupled to the recovery server 112, rather than residing in the recovery server 112. A management client residing on the recovery server 112 may then communicate with the management server 304 and other management clients in a system comprised of more than one recovery server 112, as discussed herein.

[0075] In one embodiment, a user may select an event marker corresponding with a historical view or to which recovery should be performed. The management server 304 can process the event marker and determine which historical view(s) corresponds with the event marker selected by the user. The historical view may then be provided to the user based on the event marker. As discussed herein, the user may select the event marker, provide key words or text strings associated with an event marker, provide unique identifiers related to the event marker, and so on. The management server 304 may match the event information entered by the user with the event markers in order to determine which event marker best matches the event information.

[0076] The management client 302 of the production host 102 is in communication with the management server 304 of the recovery server 112 for coordinating and managing activities within the SAN. The data interceptor 104 stores the data blocks to the primary storage 106. The data interceptor 104 communicates with the recovery server 112 in order to store the data block copies to the recovery storage 108. If the production host 102 is down, the engine 306 at the recovery server 112 can recover data block copies from the recovery storage 108 in order to provide a historical view to the alternate host 114 as requested by a user associated with the alternate host 114. The historical view may be requested by a system or a process according to some embodiments. For example, an automated process may request historical views of the data for performing offline backup.

[0077] The engine 306 coordinates activities of the data interceptor 104 via communication with the data interceptor 104. In one embodiment, the engine 306 coordinates the activities of more than one data interceptor 104. As discussed herein, the activities that may be coordinated by the engine 306 include instructing the data interceptor 104 where and/or how to store the data block copies and the envelopes in the recovery storage 108 and/or the envelopes in the index 110. However, any types of activities may be coordinated by the engine 306.

[0078] As discussed herein, the data interceptor 104 may reserve a section of the primary storage 106 for storage of metadata, envelopes, and/or data block copies, such as the private storage 310 shown in FIG. 3. Accordingly, as discussed herein, if the recovery storage 108 is not accessible, the data interceptor 104 can store the data block copies, a bit map, or other bookkeeping information to the private storage 310. The data block copies can then be provided to the recovery storage 108 when the recovery storage 108 becomes accessible. However, according to one embodiment, the private storage 310 may be utilized for storing any information, regardless of whether the recovery storage 108 is accessible.

[0079] Furthermore, the engine 306 of the recovery server 112 can simultaneously access the recovery storage 108 while the data interceptor 104 accesses the recovery storage 108. Accordingly, the engine 306 at the recovery server 112 can retrieve the data block copies from the recovery storage 108 as other data block copies are being stored to the recovery storage 108 by the data interceptor 104. For example, the engine 306 can process requests for historical views from the alternate host 114 performing recovery operations while the engine 306 continues to process and/or provide instructions for incoming data block copies and envelopes from the production host 102.

[0080] The alternate host 114 may also include a management client 308. The management server 304 of the recovery server 112 may communicate directly with the management client 308 at the alternate host 114 to deliver historical views of the data requested by a user at the alternate host 114 back to the alternate host 114.

[0081] The engine 306 at the recovery server 112 can also communicate with the alternate host 114. The engine 306 may deliver the data requested by the alternate host 114 directly to the alternate host 114. For example, a user may select an event marker representing a historical view and the engine 306 can locate the data block copies to create the historical view requested and return the historical view to the user at the alternate host 114.

[0082] FIG. 4 shows an exemplary schematic diagram for recovery server 112 coordination of historical views. One or more envelopes arrive at the recovery server 112 via a target mode driver (TMD) 402. The TMD 402 responds to commands for forwarding the envelopes. Alternatively, any type of driver may be utilized for communicating the envelopes to the recovery server 112.

[0083] The envelopes may be forwarded by the data interceptor 104 utilizing a proprietary protocol 404, such as the Mendocino Data interceptor Protocol (MDTP). A client manager 406 may be provided for coordinating the activities of the recovery server 112. The envelopes are utilized by the recovery server 112 to construct a recovery index 408. The recovery index 408 is then copied to the index 110 (FIG. 1) associated with the recovery storage 108 (FIG. 1). In order to update the index 110, the recovery index 408 may be updated and copied each time new envelopes arrive at the recovery server 112 or the recovery server 112 may update the index 110 with the new envelope information at any other time.

[0084] Optionally, a cleaner 410 defragments the data block copies and any other data that is stored in the recovery storage 108. As another option, a mover 412 moves the data block copies (i.e. the snapshots) in the recovery storage 108 and can participate in moving the data block copies between the recovery storage 108, the production host 102, the alternate hosts 114 (FIG. 1), and/or any other devices.

[0085] A recovery storage control logic 414 manages storage of the envelopes and the data block copies in the recovery storage 108 using configuration information generated by a configuration management component 416. A disk driver 418 then stores (e.g., writes) the envelopes and the data block copies to the recovery storage 108.

[0086] When a user requests a historical view of the data, as discussed herein, a historical view component 420 retrieves the data block copies needed to provide the historical view requested by a user. The user may request the historical view based on an event marker or any other criteria. Specifically, the historical view component 420 references the recovery index 408 or the index 110 pointing to the data block copies in the recovery storage 108. The historical view component 420 then requests the data block copies, corresponding to the envelopes in the index 110, from the recovery storage control logic 414. The disk driver 418 reads the data block copies from the recovery storage 108 and provides the data block copies to the historical view component 420. The data block copies are then provided to the user at the alternate host 114 that requested the data.

[0087] As discussed herein, according to one embodiment, the historical view may be constructed utilizing the data block copies from the recovery storage 108 and the data blocks from the primary storage 106. Thus, the data block copies may be utilized to construct a portion of the historical view while the data blocks may be utilized to construct a remaining portion of the historical view.

[0088] The user of the historical view may utilize the historical view to generate additional data blocks, as discussed herein. Copies of the data blocks may then be stored in the recovery storage 108 along with corresponding envelopes. The recovery server 112 then updates the index 110 and/or the branching data structure to include references to the new data block copies. Accordingly, the new data block copies are tracked via the index 110 in relation to other data block copies already stored in the recovery storage 108. One or more event markers may be associated with the new data block copies, as the copies are generated or at any other time. As discussed herein, the event markers may be directly associated with the new data block copies, or they event markers may be indirectly associated with the new data block copies. According to some embodiments, generating the new data block copies constitutes an event to associate with an event marker, itself.

[0089] By creating the branching data structure to reference the index 110, modifications to the data are stored along with the original data upon which those modifications are based. Modifications can continue to be stored as the modifications relate to the data upon which the modifications are based, so that a hierarchical relationship is organized and mapped. By using the branching data structure, the various data block copies relationship to one another can be organized at a higher level than the index 110. The branching data structure and the index 110 may comprise a single structure according to some embodiments. According to further embodiments, the branching data structure, the index 110, and/or the data block copies may comprise a single structure.

[0090] The branches in the branching data structure may be created when the historical views are modified, or when data blocks from the primary storage 106 are removed or rolled back to a point in time (i.e. historical view). The event markers may be inserted on the branches after the branches are generated. The data interceptor 104 functionality, as discussed herein, may be provided by any components or devices. Branching tree structures and the process of generating event markers is described in further detail in co-pending U.S. application Ser. No. 11/166,690, entitled “Systems and Methods for Organizing and Mapping Data,” filed on Jun. 23, 2005, and co-pending U.S. application Ser. No. 11/215,958, entitled “Systems and Methods for Event Driven Recovery Management,” filed on Aug. 30, 2005.

[0091] In some embodiments, a historical view component, such as the historical view component 420 discussed herein, residing at the recovery server 112 may provide historical views to an alternate server, such as the alternate host 114 discussed herein or any other device. The alternate server may then utilize the historical view to generate additional data blocks. For example, the alternate server may write data on top of the historical view. The additional data blocks may be generated by the alternate server using the historical view component at the recovery server 112. The historical view component may then generate envelopes and store the envelopes in the recovery server 112, as well as update the index 110 accordingly. Thus, the historical view component in some embodiments provides functions similar to the functions that may be provided by the data interceptor 104. In other embodiments, the historical view component resides outside of the recovery server 112, but is coupled to the recovery server 112 and the recovery storage 108 in order to provide functionalities similar to the data interceptor 104. Further, the production host 102 and the alternate server may comprise a single device according to some embodiments. As discussed herein, the primary storage 106 and the recovery storage 108 may comprise one storage medium according to some embodiments. Historical views are further described within co-pending U.S. application Ser. No. 11/216,874, entitled “Systems and Methods for Rapid Presentation of Historical Views of Stored Data,” filed on Aug. 30, 2005.

[0092] In other embodiments, the production host 102 includes a historical view component and a data interceptor 104, both residing on the production host 102. However, the historical view component and/or the data interceptor 104 may reside outside of, but be coupled to, the production host 102 in other embodiments. Further, the historical view component and the data interceptor 104 may comprise one component in some embodiments. The generation of envelopes, data blocks, data block copies, indexes, and so forth may be performed by the historical view component and/or the data interceptor 104 at the production host 102 in such an embodiment.

[0093] As discussed herein, the historical view component may request data blocks from the primary storage 106 and/or data block copies from the recovery storage 108 in order to generate the historical view. Further, the additional data blocks generated utilizing the historical view (i.e. on top of the historical view) may be stored to either the primary storage 106, the recovery storage 108, or to both the primary storage 106 and the recovery storage 108.

[0094] A management center 422 may also be provided for coordinating the activities of one or more recovery servers 112, according to one embodiment.

[0095] Although FIG. 4 shows the recovery server 112 having various components, the recovery server 112 may include more components or fewer components than those listed and still fall within the scope of various embodiments.

[0096] FIG. 5 shows an exemplary flow diagram for backing up data in accordance within one embodiment. In one example of these methods, memory addresses within recovery storage 108 are assigned to data block copies captured from the production host 102 or the primary storage 106 in FIG. 1. Memory addresses from the primary storage 106 (FIG. 1) associated with the original data blocks as well as the memory addresses from the recovery storage 108 are sent to the recovery server 112 (FIG. 1). The data block copies can be sent to the recovery storage 108.

[0097] At step 502, one or more first memory addresses within a recovery storage 108 are assigned to one or more data blocks. The one or more data blocks may be data blocks, data block copies, or any other kind of data that are either currently or will be stored within the primary storage 106. The one or more first memory addresses may refer to physical or virtual locations within a recovery storage medium. The recovery storage 108 may contain one or more recovery storage mediums. In some embodiments, the one or more first memory addresses are pointers that are associated to memory addresses within the recovery storage 108.

[0098] In some embodiments, the data interceptor 104 (FIG. 1) assigns the one or more first memory addresses to the one or more data blocks. In other embodiments, the recovery server 112 or the recovery storage 108 assigns the one or more first memory addresses to the one or more data blocks and sends the one or more first memory addresses to the data interceptor 104. Any device or component may assign the one or more first memory addresses to the one or more data blocks.

[0099] At step 504, one or more second memory addresses within the primary storage 106 associated with the one or more data blocks and the one or more first memory addresses are sent to the recovery server 112. In another example, the one or more second memories addresses and the one or more first memory addresses are sent to the primary storage 106. The one or more second memory addresses may refer to physical or virtual locations within the primary storage 106. In some embodiments, the one or more second memory addresses are pointers that are associated with memory addresses within the primary storage 106.

[0100] In some embodiments, the data interceptor 104 captures the data blocks as well as the second memory addresses, where the data blocks are either copied or will be copied within the primary storage 106. In other embodiments, the data interceptor 104, recovery server 112 or the recovery storage 108 assigns the one or more second memory addresses to the one or more data blocks. Any device or component may assign the one or more second memory addresses to the one or more data blocks.

[0101] The data interceptor 104 can send the one or more second memory addresses and the one or more first memory addresses to the recovery server 112. In other embodiments, the data interceptor 104 can send the one or more second memory addresses and the one or more first memory addresses to the recovery storage 108 or the index 110 (FIG. 1).

[0102] At step 506, the one or more data blocks are copied to the one or more first memory addresses within the recovery storage 108. In one example, the data interceptor 104 can copy the one or more data blocks to the recovery storage 108. In another example, the data interceptor 104 can copy the one or more data blocks to the recovery server 112.

[0103] In some embodiments, the data interceptor 104 captures commands and/or new data from a structured query language (SQL) application. In one example, the data interceptor 104 can capture new data from the application as well as SQL commands that may overwrite the data contained within the primary storage 106. The data interceptor 104 can capture the changes to the data within the primary storage 106, and assign the changes to the first memory addresses within the recovery storage 108. The data interceptor 104 may then send the second memory addresses where the changes have been stored within the primary storage 106 as well as the first memory addresses, to the recovery server 112. The changes are then copied to the second memory addresses within the recovery storage 108. Those skilled in the art will appreciate that this process may be used for any query language.

[0104] FIG. 6 shows another exemplary flow diagram for providing back up data in accordance within one embodiment. In one example of these methods, the data interceptor 104 captures and copies data blocks from the production host 102 identified in FIG. 1. The data interceptor 104 also receives the memory addresses where the data blocks are stored (or to be stored) in the primary storage 106 (FIG. 1). The data interceptor 104 further assigns memory addresses within the recovery storage 108 (FIG. 1) where the data block copies will be stored, and generates envelopes. Envelopes comprise metadata including the memory addresses within primary storage 106 associated with the data blocks as well as the memory addresses within recovery storage 108 where the copied data blocks will be stored. The envelopes are sent from the data interceptor 104 to the recovery server 112 (FIG. 1). Data block copies are sent from the data interceptor 104 to the recovery storage 108.

[0105] At step 602, the one or more first memory addresses within a recovery storage medium are sent to the data interceptor 104. In one embodiment, the recovery server 112 can maintain a map of first memory addresses that are unused within the recovery storage 108. The recovery server 112 can select one or more first memory addresses and send the one or more first memory addresses to the data interceptor 104, for example, in a freelist command. A freelist command indicates the first memory addresses within the recovery storage 108 that may receive data block copies.

[0106] The freelist command may be sent from the recovery server 112 to the alternate host 114 (FIG. 1), or the recovery storage 108 as well. In another example, the recovery storage 108 can generate and send the freelist command to the data interceptor 104, the recovery server 112, or the alternate host 114. The freelist command may be generated and sent by any component of FIG. 1.

[0107] At step 604, second memory addresses within the primary storage 106 associated with one or more data blocks are received. In one example, the data interceptor 104 or the recovery server 112 captures the second memory addresses from the production host 102. In another example, the data interceptor 104 examines the primary storage 106 to determine the second memory addresses that were most recently used. In some embodiments, the envelopes command is generated and comprises the second memory addresses.

[0108] At step 606, the one or more first memory addresses are associated with the one or more data blocks. In one example, the data interceptor 104 receives the freelist command from the recovery server 112. The data interceptor 104 can associate at least one of the one or more first memory addresses from the freelist command to the data blocks and include the at least one of the one or more first memory addresses associated with the data blocks within the envelopes command.

[0109] At step 608, the one or more first memory addresses and the one or more second memory addresses are sent to the recovery server 112. In one example the one or more second memory addresses received in step 604 and the at least one of the one or more first memory addresses are included within the envelopes command and sent to the recovery server 112. In other examples, the envelopes command can be sent from the data interceptor 104 to the recovery storage 108 and/or the index 110.

[0110] At step 610, one or more data blocks are copied to the recovery storage 108. In one example, the data blocks which were stored within the one or more second memory addresses within the primary storage 106 are copied and sent to the recovery storage 108. In other embodiments, the data blocks are copied and sent to a recovery server 112 and/or an index 110. In another example, the data may be included in a store data command which is sent from the data interceptor 104. A store data command is a message that includes data blocks to copied between two components of FIG. 1. For example a store data command may be a message that includes data blocks to be copied from the data interceptor 104 to the recovery storage 108. In another example, the store data command may be a message that includes data blocks to be copied between the recovery storage 108 to the data interceptor 104 so that the data blocks are ultimately copied to the primary storage 106.

[0111] FIG. 7 and FIG. 10 show exemplary diagrams for an envelopes command and a freelist command, respectively, in accordance with one embodiment. The envelopes command and freelist command are messages that may be sent between the various components identified in FIG. 1. For example, the data interceptor 104 (FIG. 1) can send the envelopes command to the recovery server 112 (FIG. 1). In another example, the recovery server 112 may send the freelist command to the data interceptor 104.

[0112] Many messages comprise common fields that contain data to perform similar functions. Some examples of common fields include a command/response (CR) field, a silent field, a command field, a task ID field, and a total length in bytes.

[0113] Many messages comprising a CR within the CR field can be sent between different components identified in FIG. 1. The CR indicates whether the message is a command or response. In one example, the CR is a non-zero value which may indicate that the message is a command while a value of zero indicates that the message is a response to a prior command.

[0114] Many messages can also comprise a silent field containing the silent data. The silent data indicates whether the message requires a response. In one example, the value of the silent data is zero which may indicate that the receiver of the message is required to send a response. If the value of the silent data is not zero, then the receiver of the message may not be required to send a response.

[0115] Messages may further comprise a command field containing command data. The command data indicates what command the message may be. For example, the value of command data may be “0x18” to indicate that the message is an envelopes command. In another example, the value of the command data may be “0x011” to indicate that the message is a freelist command. There may be any number of values to indicate any number of commands.

[0116] A Task ID is data that identifies a particular command or response. For example, a command with a unique task ID may be sent from the data interceptor 104 to the recovery server 112. The recovery server 112 may send a response with the same unique task ID to identify the response as being associated to the previous command. The Task ID may also allow a receiver of similar commands to distinguish the messages. For example, the recovery server 112 may receive multiple envelopes commands. Each envelopes command may comprise a different Task ID.

[0117] A total length in bytes indicates the number of bytes that are within the message. In some embodiments, the total length in bytes may indicate the number of bits or any other measure of the quantity of data associated with a message.

[0118] FIG. 7 shows an exemplary diagram for an envelopes command in accordance with one embodiment. The envelopes command is the command that contains one or more envelopes which indicate one or more first memory addresses within the recovery storage 108 (FIG. 1) associated with data blocks and one or more second memory addresses within the primary storage 106 (FIG. 1) associated with data blocks. In one example, the data interceptor 104 or the alternate host 114 can send the envelopes command to the recovery server 112 in FIG. 1. In another example, the recovery server 112 can send the envelopes command to the index 110 (FIG. 1). The envelopes command may comprise a CR 700, a silent 702, a command 704, a task ID 706, a total length in bytes 708, a UUID of view 710, a count of total envelopes 712, an envelopes header structure 714, and an array of envelopes detail structures 716.

[0119] The CR 700, the silent 702, the command 704, the task ID 706, and the total length in bytes 708 are common data types found in many messages. These data types are further described herein. The CR 700 comprises data that indicates that the message is an envelopes command. The silent 702 may comprise data that indicates that the envelopes command does not require a response. In another embodiment, the silent 702 may comprise data that indicates that the envelopes command requires a response. The command 704 comprises data that indicates that the message is an envelopes command.

[0120] The task ID 706 is data that further identifies a particular envelopes command. In one example, the recovery server 112 receives multiple envelopes commands. The task ID 706 of each envelopes command may be different and allows the recovery server 112 to track the envelopes. A total length in bytes 708 indicates the number of bytes within the envelopes command.

[0121] The universally unique identifier (UUID) of view 710 within a UUID of view field indicates a UUID associated with one or more primary storages 106. In other examples, a UUID of view 710 may also an image of one or more primary storages 106 that is presented to the alternate host 114.

[0122] The count of total envelopes 712 within a count of total envelopes field, indicates a number of envelopes associated with the array of envelopes detail structure 716. In some embodiments, the count of total envelopes 712 may represent a range of envelopes. For example, a value of 1 within the count of total envelopes 712 may represent one to ten envelopes within the array of envelopes detail structure 716, while a value of 2 may represent ten to twenty envelopes.

[0123] The envelopes header structure 714 within an envelopes header structure field, contains a summary of the data in the envelopes command as well as data that is common to all of the envelopes associate with the array of envelopes detail structure 716.

[0124] The array of envelopes detail structure 716 within an array of envelopes detail structure field contains an array of envelopes that describe write operations that the production host 102 (FIG. 1) has performed or will be performing. The array of envelopes detail structure 716 is further discussed in FIG. 8

[0125] FIG. 8 shows an exemplary diagram for an array of envelopes detail structure 716 within an envelopes command in accordance with one embodiment. The array of envelopes detail structure 716 comprises a generation stamp 800, a detail structure 802, an array of envelope structures 804, and a padding 806.

[0126] The generation stamp 800 within a generation stamp field is an identifier associated with the envelopes command. In one example, the generation stamp 800 can indicate when the envelopes command was generated. In another example, the generation stamp 800 can indicate when the data in the envelope was placed within the envelopes command or when the data was sent.

[0127] The detail structure 802 contained within a detail structure field may identify and describe the array of envelope structures 804 and may contain such information including a type of data structure, and a number of elements. The detail structure 802 may further describe common elements within the array of envelope structures 804.

[0128] The array of envelope structures 804 within an array of envelope structures field comprises envelopes within the envelopes command. The array of envelope structures 804 is further described in FIG. 9.

[0129] The padding 806 within a padding field contains bytes necessary to ensure that the array of envelopes detail structures is a certain size to allow the array of envelopes detail structures to be read within one atomic operation.

[0130] FIG. 9 shows an exemplary diagram for the array of envelope structures field within an envelopes command in accordance with one embodiment. The array of envelopes structure 804 within the array of envelopes structure field comprises a volume universally unique identifier (UUID) 900, a CanID 902, a logical block address (LBA) 904, a segment group number 906, a segment number 908, an offset in segment 910, a timestamp 912, a length 914, a sequence number 916, and flags 918.

[0131] The volume UUID 900 within a volume UUID field indicates an UUID of a volume of primary storage 106 that the application wrote to. In some embodiments, the application writes to a specific volume within a SCSI hard drive contained in the primary storage 106. The volume is associated with a specific UUID which is identified in the volume UUID field.

[0132] The CanID 902 within a CanID field is a UUID that associates a set of envelopes. The CanID 902 can span multiple envelopes within an envelopes command, or multiple envelopes within several envelopes commands.

[0133] The LBA 904 within a logical block address (LBA) field indicates the sequential address for data blocks written to primary storage 106 by the application. The LBA 904 may refer to the address of data blocks written by the application to any kind of primary storage 106, including SCSI, RAM, or a database. Primary storage 106 is further discussed herein.

[0134] The segment group number 906 within the segment group number field is associated with a specific storage device within the recovery storage 108 (FIG. 1) where the data block copies are to be written to. In some embodiments, the segment group number 906 is a UUID of one or more recovery storages 108.

[0135] The segment number 908 and the offset in segment 910 together refer to a physical address within the recovery storage 108 where the data blocks associated with the envelopes may be stored. The segment number 908 within a segment number field refers to a region of recovery storage 108 within a segment group. In one example, the segment number 908 is a segment that is associated with memory addresses where data is to be stored within the recovery storage 108. The offset in segment 910 is associated with the segment number 908 and indicates a position within the segment or memory addresses within the recovery storage 108. In some embodiments, the segment number field and the offset in segment field are combined into a single field.

[0136] The timestamp 912 within a timestamp field indicates a time on the production host 102 when a write operation was performed. In another embodiment, the timestamp 912 indicated a time on the recovery server 112 or any other time. The timestamp 102 may be a sixty-four bit value representing the number of micro-seconds since Jan. 1, 1970 00:00:00 UTC. Alternately, the timestamp 102 can be any value associated with time.

[0137] The length 914 within a length field indicates a quantity of data written by the production host 102 (FIG. 1). In one example, the length 914 indicates a number of sectors or bytes written by an application on the production host 102.

[0138] The sequence number 916 within a sequence number field indicates an order in which the write operations occurred. In one example, the production host 102 may have clock changes. As a result, the order of the write operations may not agree with the timestamps 912. In this example, the data block copies will be written to the recovery storage 108 in an order based on the sequence number.

[0139] The flags 918 field may comprise an identifier to represent information about the envelope or the state of the data interceptor 104 at the time the envelope was generated. In one example, the flags 918 may indicate that the envelope was generated during a region recovery. A region recovery is necessary when there is a loss of connectivity between the data interceptor 104 and the recovery server 112. In one example, the data interceptor 104 indicates within the flags 918 that the buffered envelopes commands are a part of a region recovery. Once communication between the recovery server 112 and the data interceptor 104 is restored, the recovery server 112 ensures that messages between the recovery server 112 and the data interceptor 104 were not lost. The recovery server 112 proceeds to receive the buffered envelopes commands from the data interceptor 104 and track the missed or lost data.

[0140] FIG. 10 shows an exemplary schematic diagram for a freelist command in accordance with one embodiment. The freelist command is the command that contains one or more memory addresses within the recovery storage 108. The freelist command comprises a CR 1000, a silent 1002, a command 1004, a Task ID 1006, a Total Length in Bytes 1008, a UUID of the segment group 1014, a base of data region 1016, a length of data region 1018, a base of metadata region 1020, a length of metadata region 1022, a generation stamp 1024, a segment group number 1026, and a segment number 1028.

[0141] In one example, the recovery server 112 (FIG. 1) maintains a map of free memory addresses within the recovery storage 108 (FIG. 1). The recovery server 112 can allocate a portion of the free memory addresses within a freelist command and send the freelist command to the data interceptor 104 (FIG. 1). The data interceptor 104 can assign the memory addresses within the freelist command to copies of data blocks.

[0142] The CR 1000, the silent 1002, the command 1004, the task ID 1006, and the total length in bytes 1008 are common data types found in many messages. These data types are further described herein. The CR 1000 comprises data that indicates that the message is a freelist command.

[0143] The silent 1002 may comprise data that indicates that the freelist command does not require a response. In another embodiment, the silent 702 can comprise data that indicates that the freelist command requires a response. In one example, the data interceptor 104 receives a freelist command from the recovery server 112 indicating free memory addresses within the recovery storage 108. The data interceptor 104 can send an envelopes command as a response to the freelist command. The envelopes command sent from the data interceptor 104 may comprise the free memory addresses from the freelist command.

[0144] The command 1004 comprises data that indicates that the message is a freelist command. The task. ID 1006 is data that further identifies the particular freelist command.

[0145] The UUID of view 1010 within the UUID of view field indicates a UUID of a volume within the recovery storage 108 associated with the memory addresses within the freelist command.

[0146] A number of segment structures that follow 1012 within a number of segment structures that follow field, indicates a number of memory addresses within an array of free segment structures 1014. In some embodiments, the number of segment structures that follow 1012 represent one or more memory segments.

[0147] The UUID of the segment group 1014 within a UUID of the segment group field identifies a UUID of a volume of recovery storage 108 associated with the free memory addresses. In other embodiments, the UUID of the segment group 1014 may identify any unique identifier of a physical or virtual storage medium within the recovery storage 108 (FIG. 1).

[0148] The base of data region 1016 within a base of data region field identifies a base physical address of the free memory address within the recovery storage 108 (FIG. 1). The base of data region 1016 may indicate sectors or any other unit that indicates a beginning of an ordered set of free memory addresses.

[0149] The length of data region 1018 within a length of data region field identifies a length of the physical addresses of the free memory addresses within the recovery storage 108. For example, the base of data region 1016 may indicate that the free memory addresses begin at physical address “1” within the recovery storage 108. The length of data region 1018 may indicate a length of “3”. Thus, physical addresses “1”, “2”, and “3” may be contained within the freelist command. The length of data region 1018 may indicate sectors or any other unit that signifies the length of an ordered set of free memory addresses.

[0150] The base of metadata region 1020 within a base of metadata region field identifies a physical or virtual memory address within the index 110 (FIG. 1). The metadata region field may be the location where the metadata and/or envelopes are stored. The base of metadata region 1020 may indicate sectors or any other unit that denotes a beginning of an ordered set of free memory addresses.

[0151] The length of metadata region 1022 within a length of metadata region field identifies a length of the physical or virtual addresses of the memory addresses within the index 110 or the recovery server 112 (FIG. 1).

[0152] The generation stamp 1024 within a generation stamp field indicates a number of elements within an array of free segment structures 1014. The generation stamp 1024 within a generation stamp field is an identifier associated with the freelist command.

[0153] The segment group number 1026 within a segment group number field is associated with a specific storage device within the recovery storage 108 where the data block copies are to be written to. In some embodiments, the segment group number 1026 is a UUID of one or more recovery storages 108. The segment group number 1026 may identify any storage device where data block copies are written within the recovery storage 108.

[0154] The segment number 1028 refers to the physical address within the recovery storage 108 where the data blocks associated with the memory addresses may be stored. The segment number 1028 within the segment number field may refers to a region of recovery storage 108 within a segment group.

[0155] Those skilled in the art will appreciate that the list of different fields, data, and data types of the envelopes command and the freelist command identified in FIGS. 7-11 is not exhaustive nor are all the fields, data, and data types identified necessary to perform one or more embodiments.

[0156] Many messages, fields, data, and data types within the envelopes command, freelist command, and other messages may comprise a cyclic redundancy check (CRC). The CRC is related to size of data within an associated field. The CRC may be sent with data to allow the receiving system to determine if the received data has been altered or corrupted within transmission. In one example, the recovery server 112 (FIG. 1) receives an envelopes command from the data interceptor 104 (FIG. 1). The envelopes command contains the envelopes header structure 714 (FIG. 7). A CRC associated with the envelopes header structure 714 may also be sent from the data interceptor 104 to the recovery server 112. The CRC contains the number of bits of data within the envelopes header structure 714 that was sent from the data interceptor 104. After the envelopes command is received by the recovery server 112, the recovery server 112 may check the size of the envelopes header structure 714 received against the CRC. If they match, then the recovery server 112 proceeds to perform the next operation. If they do not match, the recovery server 112 may attempt to correct for errors that occurred in transmission if the coding of the envelopes command allows, or may send a request to the data interceptor 104 to resend the envelopes command.

[0157] The above-described functions can be comprised of instructions that are stored on a storage medium. The instructions can be retrieved and executed by a processor. Some examples of instructions are software, program code, and firmware. Some examples of storage medium are memory devices, tape, disks, integrated circuits, and servers. The instructions are operational when executed by the processor to direct the processor to operate in accordance with embodiments of the invention. Those skilled in the art are familiar with instructions, processor(s), and storage medium.

[0158] The invention has been described with reference to exemplary embodiments. It will be apparent to those skilled in the art that various modifications may be made and other embodiments can be used without departing from the broader scope of the invention. Therefore, these and other variations upon the exemplary embodiments are covered by the present invention.