US 6,647,474 B2Grant

Remote data mirroring system using local and remote write pending indicators

Issue Date:2003-11-11

•20 Claims

•2 Drawing Sheets

Abstract

A primary data storage system is linked to a geographically remote secondary data storage system for automatically maintaining a remote copy of the data in the primary storage. The primary data storage system controller uses write pending indicators to control and coordinate the remote copy process. In response to receipt of data from the host computer, a first write pending indicator is set to write the data into at least one primary data storage device, and a second write pending indicator is set to copy the data to the secondary data storage system controller. The first write pending indicator is reset after the data is written to the primary data storage device, and the second write pending indicator is reset after receiving an acknowledgement back from the secondary data storage system controller.

Metadata

Assignee

EMC Corporation

Inventors

Moshe Yanai
Natan Vishlitzky
Bruno Alterescu
Daniel D. C. Castel
Gadi G. Shklarsky

Application Information

Application Number:US 10/224,138

Filing Date:2002-08-20

Priority Date:1993-04-23

Art Unit:7

Classifications

IPC:

G06F 1216H02H 305

Field of Search:

711154711156711161711162711165711 5711 6711 7711718

Patent Drawings (2 sheets)

Description

[0002] This application is a divisional of U.S. patent application Ser. No. 09/709,814 filed Nov. 10, 2000, now U.S. Pat. No. 6,502,205 which is a divisional of U.S. patent application Ser. No. 09/061,708 filed Apr. 17, 1998 (U.S. Pat. No. 6,173,377 issued Jan. 9, 2001), which is a continuation of U.S. patent application Ser. No. 08/654,511 filed May 28, 1996 (U.S. Pat. No. 5,742,792 issued Apr. 21, 1998), which is a continuation-in-part of U.S. patent application Ser. No. 08/052,039 filed Apr. 23, 1993, entitled REMOTE DATA MIRRORING (U.S. Pat. No. 5,544,347 issued Aug. 6, 1996), which are all incorporated herein by reference.

Field of the Invention

[0003] This invention relates to data storage, and more particularly, to a system and method for automatically providing and maintaining a copy or mirror of data stored at a location geographically remote from the main or primary data storage device.

Background of the Invention

[0004] Nearly all data processing system users are concerned with maintaining back-up data in order to insure continued data processing operations should their data become lost, damaged, or otherwise unavailable.

[0005] Large institutional users of data processing systems which maintain large volumes of data such as banks, insurance companies, and stock market traders must and do take tremendous steps to insure back-up data availability in case of a major disaster. These institutions recently have developed a heightened awareness of the importance of data recovery and back-up in view of the many natural disasters and other world events including the bombing of the World Trade Center in New York City.

[0006] Currently, data processing system users often maintain copies of their valuable data on site on either removable storage media, or in a secondary “mirrored” storage device located on or within the same physical confines of the main storage device. Should a disaster such as fire, flood, or inaccessibility to a building occur, however, both the primary as well as the secondary or backed-up data will be unavailable to the user. Accordingly, more data processing system users are requiring the remote storage of back-up data.

[0007] One prior art approach at data back-up involves taking the processor out of service while back-up tapes are made. These tapes are then carried off premises for storage purposes. Should access to the backed-up data be required, the proper tape must be located, loaded onto a tape drive, and restored to the host system requiring access to the data. This process is very time consuming and cost intensive, both in maintaining an accurate catalog of the data stored on each individual tape, as well as storing the large number of tapes required to store the large amounts of data required by these institutions. Additionally and most importantly, it often takes twenty-four hours before a back-up tape reaches its storage destination during which time the back-up data is unavailable to the user.

[0008] Additionally, today's systems require a significant amount of planning and testing in order to design a data recovery procedure and assign data recovery responsibilities. Typically, a disaster recovery team must travel to the test site carrying a large number of data tapes. The team then loads the data onto disks, makes the required network connections, and then restores the data to the “test” point of failure so processing can begin. Such testing may take days or even weeks and always involves significant human resources in a disaster recovery center or back-up site.

[0009] Some providers of prior art data storage systems have proposed a method of data mirroring whereby one host Central Processing Unit (CPU) or processor writes data to both a primary, as well as a secondary, data storage device or system. Such a proposed method, however, overly burdens the host CPU with the task of writing the data to a secondary storage system and thus dramatically impacts and reduces system performance.

[0010] Accordingly, what is required is a data processing system which automatically and asynchronously, with respect to a first host system, generates and maintains a backup or “mirrored” copy of a primary storage device at a location physically remote from the primary storage device, without intervention from the host which seriously degrades the performance of the data transfer link between the primary host computer and the primary storage device.

Summary of the Invention

[0011] This invention features a system which automatically, without intervention from a host computer system, controls storing of primary data received from a primary host computer on a primary data storage system, and additionally controls the copying of the primary data to a secondary data storage system controller which forms part of a secondary data storage system, for providing a back-up copy of the primary data on the secondary data storage system which is located in a geographically remote location from the primary data storage system.

[0012] Copying or mirroring of data from a primary data storage system to a secondary data storage system is accomplished without intervention of a primary or secondary host computer and thus, without affecting performance of a primary or secondary host computer system. Primary and secondary data storage system controllers are coupled via at least one high speed communication link such as a fiber optic link driven by LED's or laser.

[0013] At least one of the primary and secondary data storage system controllers coordinates the copying of primary data to the secondary data storage system and at least one of the primary and secondary data storage system controllers maintains at least a list of primary data which is to be copied to the secondary data storage device.

[0014] Additionally, the secondary data storage system controller provides an indication or acknowledgement to the primary data storage system controller that the primary data to be copied to the secondary data storage system in identical form as secondary data has been received or, in another embodiment, has actually been written to a secondary data storage device.

[0015] Accordingly, data may be transferred between the primary and secondary data storage system controllers synchronously, when a primary host computer requests writing of data to a primary data storage device, or asynchronously with the primary host computer requesting the writing of data to the primary data storage system, in which case the remote data copying or mirroring is completely independent of and transparent to the host computer system.

[0016] At least one of the primary data storage system controller and the secondary data storage system controller maintains a list of primary data which is to be written to the secondary data storage system. Once the primary data has been at least received or optionally stored on the secondary data storage system, the secondary data storage system controller provides an indication or acknowledgement of receipt or completed write operation to the primary data storage system.

[0017] At such time, the primary and/or secondary data storage system controller maintaining the list of primary data to be copied updates this list to reflect that the given primary data has been received by and/or copied to the secondary data storage system. The primary or secondary data storage system controllers and/or the primary and secondary data storage devices may also maintain additional lists for use in concluding which individual storage locations, such as tracks on a disk drive, are invalid on any given data storage device, which data storage locations are pending a format operation, which data storage device is ready to receive data, and whether or not any of the primary or secondary data storage devices are disabled for write operations.

[0018] Thus, an autonomous, host computer independent, geographically remote data storage system is maintained providing a system which achieves nearly 100 percent data integrity by assuring that all data is copied to a geographically remote site, and in those cases when a back-up copy is not made due to an error of any sort, an indication is stored that the data has not been copied, but instead must be updated at a future time.

[0019] Such a system is provided which is generally lower in cost and requires substantially less manpower and facilities to achieve than the prior art devices.

[0020] The present invention more particularly concerns the use of write pending indicators by the primary data storage system controller. In response to receipt of data from the host computer, a first write pending indicator is set to write the data into at least one primary data storage device, and a second write pending indicator is set to copy the data to the secondary data storage system controller. The first write pending indicator is reset after the data is written to the primary data storage device, and the second write pending indicator is reset after receiving an acknowledgement back from the secondary data storage system controller.

Brief Description of the Drawings

[0021] These and other features and advantages of the present invention will be better understood when read together with the following drawings wherein:

[0022] FIG. 1 is a block diagram illustrating the system with remote data mirroring according to the present invention;

[0023] FIG. 2 is a schematic representation of a portion of an index or list maintained by the system of the present invention to determine various features including which primary data has been copied to a secondary disk; and

[0024] FIG. 3 is a schematic representation of an additional list or index maintained by the system of the present invention to keep track of additional items including an invalid data storage device track, device ready status and write disable device status.

Description of Illustrative Embodiments

[0025] The present invention features a system which provides a geographically remote mirrored data storage system which contains generally identical information to that stored on a primary data storage system. Utilizing such a system, data recovery after a disaster is nearly instantaneous and requires little, if any, human intervention. Using the present system, the data is retrieved from a remote device through the host data processing system.

[0026] A system in accordance with the present invention is shown generally at 10, FIG. 1, and includes at site A, which is a first geographic location, a host computer system 12 as is well known to those skilled in the art. The host computer system 12 is coupled to a first and primary data storage system 14. The host 12 writes data to and reads data from the primary data storage system 14.

[0027] The primary data storage system 14 includes a primary data storage system controller 16 which receives data from the host 12 over data signal path 18. The primary data storage system controller 16 is also coupled to a storage device 20 which may include a plurality of data storage devices 22a-22c. The storage devices may include disk drives, optical disks, CD's or other data storage devices. The primary system controller 16 is coupled to the storage device 20 by means of data signal path 24.

[0028] The primary data storage system controller 16 includes at least one channel adapter (C.A.) 26 which is well known to those skilled in the art and interfaces with host processing system 12. Data received from the host is typically stored in cache 28 before being transferred through disk adapter (D.A.) 30 over data signal path 24 to the primary storage device 20. The primary data storage controller 16 also includes a data director 32 which executes one or more sets of predetermined micro-code to control data transfer between the host 12, cache memory 28, and the storage device 20. Although the data director 32 is shown as a separate unit, either one of a channel adapter 26 or disk adapter 30 may be operative as a data director, to control the operation of a given data storage system controller. Such a reconfigurable channel adapter and disk adapter is disclosed in Applicant's U.S. Pat. No. 5,335,352 entitled RECONFIGURABLE, MULTI-FUNCTION DATA STORAGE SYSTEM CONTROLLER SELECTIVELY OPERABLE AS AN INPUT CHANNEL ADAPTER AND A DATA STORAGE UNIT ADAPTER, which is fully incorporated herein by reference.

[0029] The primary data storage system 14 according to one embodiment of the present invention also includes a service processor 34 coupled to the primary data storage system controller 16, and which provides additional features such as monitoring, repair, service, or status access to the storage system controller 16.

[0030] The primary data storage system controller 16 of the present invention also features at least a second disk adapter 36 coupled to the internal bus 38 of the primary data storage system controller 16. The second disk adapter 36 is coupled, via a high speed communication link 40 to a disk adapter 42 on a secondary data storage system controller 44 of a secondary data storage system 46. Such high speed, point-to-point communication links between the primary and secondary data storage system controllers 16 and 44 include a fiber optic link driven by an LED driver, per IBM ESCON standard; a fiber optic link driven by a laser driver, and optionally T1 and T3 telecommunication links. Utilizing network connections, the primary and secondary data storage system controllers 16 and 44 may be connected to FDDI networks, T1 or T3 based networks and SONET networks.

[0031] The secondary data storage system 46 is located at a second site geographically removed from the first site. For this patent application, “geographically removed site” means not within the same building as the primary data storage system. There are presently known data processing systems which provide data mirroring to physically different data storage systems. The systems, however, are generally within the same building. The present invention is directed to providing complete data recovery in case of disaster, such as when a natural disaster such as a flood or a hurricane, or man-made disasters such as fires or bombings destroy one physical location, such as one building.

[0032] As in the case of the primary data storage system, the secondary data storage system 46 includes, in addition to the secondary data storage system controller 44, a secondary data storage device 48 including a plurality of storage devices 50a-50c. The plurality of storage devices on the secondary data storage system 46, as well as the primary data storage system 14, may have various volumes and usages such as a primary data storage device 50awhich is primary with respect to the attached storage controller 44 and host 52 in the case of the secondary data storage system 46, and the primary storage device 22awhich is primary with respect to the first or primary host 12 in the case of the primary data storage system 14.

[0033] Additionally, each storage device, such as storage device 48, may include a secondary storage volume 50bwhich serves as the secondary storage for the primary data stored on the primary volume 22aof the primary data storage system 14. Similarly, the primary data storage system 14 may include a secondary storage volume 22bwhich stores primary data received and copied from the secondary site and data storage system 46 and host 52.

[0034] Additionally, each storage device 20, 48, may include one or more local volumes or storage devices 22c, 50c, which are accessed only by their locally connected data processing systems.

[0035] The secondary storage system controller 44 also includes at least a first channel adapter 54 which may receive data from an optionally connected secondary host 52 or an optionally connected hotsite host or CPU 56. Optionally, the primary host 12 may include a data signal path 58 directly into the channel adapter 54 of the secondary data storage system 46, while the optional secondary host 52 may include an optional data path 60 into the channel adapter 26 of the primary data storage system 14. Although the secondary host 52 illustrated in FIG. 1 is not required for remote data mirroring as described in the present patent application, such a host would be required for data retrieval if both the primary host 12 as well as the primary data storage system 14 would be rendered inoperative. Similarly, a hotsite host or CPU 56 may optionally be provided at a third geographically remote site to access the data stored in the secondary data storage system 46.

[0036] The high speed link 40 between the primary and secondary data storage systems 14 and 46 is designed such that multiple links between the primary and secondary storage system may be maintained for enhanced availability of data and increased system performance. The number of links is variable and may be field upgradeable. Additionally, the service processor 34 of the primary data storage system 14 and the service processor 62 of the secondary data storage system 46 may also be coupled to provide for remote system configuration, remote software programming, and to provide a host base point of control of the secondary data storage system.

[0037] The secondary data storage system controller 44 also includes cache memory 64 which receives data from channel adapter 54 and disk adapter 42, as well as disk adapter 66 which controls writing data to and from secondary storage device 48. Also provided is a data director 68 which controls data transfer over communication bus 70 to which all the elements of the secondary data storage system controller are coupled.

[0038] An additional feature of the system 10 of FIG. 1 is the ability to dynamically reconfigure channel adapters as disk adapters and disk adapters as channel adapters, as described in Applicant's U.S. Pat. No. 5,269,011 entitled DYNAMICALLY RECONFIGURABLE DATA STORAGE SYSTEM WITH STORAGE SYSTEM CONTROLLERS SELECTIVELY OPERABLE AS CHANNEL ADAPTERS OR STORAGE DEVICE ADAPTERS, which is fully incorporated herein by reference.

[0039] The primary and secondary data storage systems may optionally be connected by means of currently available, off-the-shelf channel extender equipment using bus and tag or ESCON interfaces.

[0040] The data storage system 10 of FIG. 1 is designed to provide the copying of data from a primary data storage system to a physically remote secondary data storage system transparent to the user, and external from any influence of the primary host which is coupled to the primary data storage system. The system 10 of FIG. 1 is designed to operate in at least two modes, the first being a real-time or synchronous mode wherein the primary and secondary storage systems must guarantee that the data exists and is stored in two physically separate data storage units before input/output completion; that is, before channel end and device end is returned to the primary host. Alternatively, the system 10 of FIG. 1 is designed to operate in a point-in-time or asynchronous mode wherein the data is copied to the remote or secondary data storage system asynchronously from the time when the primary or local data processing system returns the input/output completion signal (channel end and device end) to the primary host. This eliminates any performance penalty if the communication link between the primary and secondary data storage systems is too slow, but creates the additional needs to manage the situation where data is not identical or in “sync” between the primary and secondary data storage systems.

[0041] Thus, in the real time or synchronous mode, the primary data storage system automatically controls the duplication or copying of data to the secondary data storage system controller transparently to the primary host computer. Only after data is safely stored in both the primary and secondary data storage system, as detected by an acknowledgement from the secondary storage system to the primary storage system, does the primary data storage system acknowledge to the primary host computer that the data is synchronized. Should a disaster or facility outage occur at the primary data storage system site, the user will simply need to initialize the application program in the secondary data storage system utilizing a local host (52) or a commercial hotsite CPU or host 56.

[0042] The link between the primary and secondary storage system controllers 14 and 46 may be maintained in a unidirectional mode wherein the primary data storage system controller monitors and controls data copying or mirroring. Alternatively, a bi-directional implementation may be used wherein either controller can duplicate data to the other controller, transparently to the host computer. Should a disaster or facilities outage occur, recovery can be automatic with no human intervention since the operational host computer already has an active path (40, 58, 60) to the data through its local controller. While offering uninterrupted recovery, performance will be slower than in an unidirectional implementation due to the overhead required to manage intercontroller tasks.

[0043] In the second, point-in-time mode of operation, the primary data storage system transparently duplicates data to the secondary data storage system after the primary data storage system acknowledges to the host computer, via channel end and device end, that the data has been written to the storage device and the input/output operation has been completed. This eliminates the performance impact of data mirroring over long distances. Since primary and secondary data are not synchronized, however, the primary data storage system must maintain a log file of pending data which has yet to be written to the secondary data storage device. Such data may be kept on removable, non-volatile media, in the cache memory of the primary or secondary data storage system controller as will be explained below, or in the service processor 34, 62.

[0044] Accordingly, a feature of the system 10 of FIG. 1 is the ability of a data storage system to control the transfer or copying of data from a primary data storage system to the secondary data storage system, independent of and without intervention from one or more host computers. Most importantly, in order to achieve optimum data mirroring performance, such data mirroring or copying should be performed asynchronously with input/output requests from a host computer. Accordingly, since data will not be immediately synchronized between the primary and secondary data storage systems, data integrity must be maintained by maintaining an index or list of various criteria including a list of data which has not been mirrored or copied, data storage locations for which a reformat operation is pending, a list of invalid data storage device locations or tracks, whether a given device is ready, or whether a device is write-disabled. Information must also be included as to the time of the last operation so that the data may later be synchronized should an error be detected.

[0045] A feature of the system 10 of FIG. 1 is that both the primary or secondary data storage systems maintain a table of the validity of data in the other storage system. As disclosed in U.S. Pat. No. 5,206,939 entitled SYSTEM AND METHOD FOR DISK MAPPING AND DATA RETRIEVAL, which is fully incorporated herein by reference, the present system maintains a list or index, utilizing one or more flag bits, in a hierarchical structure, on each physical and logical data storage device.

[0046] In the system 10 of FIG. 1, however, such information is kept on both devices for each individual system as well as the other data storage system. Thus, as illustrated in FIG. 2 in the partial list or table 100, each data storage system maintains an indication of write or copy pending 102 of both the primary data (M1) 104, and the secondary data (M2) 106. Similarly, an index is maintained of a pending format change since a disk format change may be accomplished. The format pending bits 108 including a first primary bit 110 and a second secondary bit 112 indicate that a format change has been requested and such change must be made on the disk.

[0047] Thus, when a host computer writes data to a primary data storage system, it sets both the primary and secondary bits 104, 106 of the write pending bits 102 when data is written to cache. For these examples, the M1 bit will refer to the primary data storage system and the M2 bit will refer to the secondary data storage system. When the primary data storage system controller's disk adapter writes the data to the primary data storage device, it will reset bit 104 of the write pending indicator bits 102. Similarly, once the secondary data storage system has written the data to the secondary data storage device, the secondary data storage write pending indicator bit 106 will be reset.

[0048] The service processors in one embodiment of the present invention will periodically scan the index table for write pending indicator bits and invoke a copy task which copies the data from the primary data storage device to the secondary. In addition, one or more of the spare index or table bits 114, 116 may be utilized to store other data such as time stamp, etc.

[0049] In addition to the write pending and format pending bits described above, the system 10 also includes several additional general purpose flags to assist in error recovery. As shown in FIG. 3, invalid track flags 120 including primary bit 122 and secondary bit 124 are utilized and maintained on each data storage device to indicate that the data storage location such as a track, does not contain valid data. Another background task running on the data storage system such as in the service processor constantly checks invalid track bits on each data storage device, and if a bit is found to be set, the copy task is invoked to copy the data from the known good device to the device with the invalid flag track set. Additional flags may be provided such as the device ready flags 126 including bits 128 and 130 which serve to indicate that the device is ready. Similarly, write disable flags 132 may be provided which indicate that a particular primary device or drive 134 or secondary device or drive 136 can presently not be written to. Data can still be copied to the good or enabled drive and then later copied to the disabled drive. If one drive or device is bad, the system 10 of FIG. 1 will set all tracks of that drive as not valid to later cause a copy of all the data.

[0050] Accordingly, each data storage device keeps data validity information about its mirrored device. If for some reason a device is not accessible, either the primary or the secondary device, every new write command goes to the accessible mirrored device along with information that the not accessible device has a track which is not valid. As soon as the non-accessible device becomes accessible, then automatically, as a background operation, the drives re-synchronize. In the case when a specific track is not shown on both the primary and secondary storage system, an indication of such will be assigned and the user will be alerted. A utility operating on the service processors will give the user a report of all the non-valid (out of sync) tracks. This report can be transferred from one site to another over the link 63, FIG. 1, that connects the two service processors 34, 62.

[0051] Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the claims which follow.

Claims

What is claimed is:

1. A remote copy system for automatically providing a remote copy of data from a host computer, said system comprising:

a first data storage system including a first data storage system controller and at least one first data storage device, the first data storage system controller having a first cache memory, the first data storage system controller receiving the data from the host computer and initially storing the data in the first cache memory and subsequently writing the data into said at least one first data storage device; and

a second data storage system located remote from the first data storage system, the second data storage system including a second data storage system controller and at least one second data storage device, the second data storage system controller having a second cache memory, the first data storage system controller being coupled to the second data storage system controller for copying the data from the first data storage system controller to the second data storage system controller, the second data storage system controller storing the data in the second cache memory and writing the data into said at least one second data storage device to produce the remote copy of the data from the host computer;

the first data storage system controller coordinating and controlling the copying of the data to the second data storage system controller wherein, in response to receipt of the data from the host computer, a first write pending indicator is set to write the data into said at least one first data storage device, and a second write pending indicator is set to copy the data to the second data storage system controller, the first write pending indicator being reset after the data is written to said at least one first data storage device and the second write pending indicator being reset after receiving an acknowledgement back from the second data storage system controller.

2. The remote copy system as claimed in claim 1, wherein the acknowledgement back from the second data storage system controller indicates that the second data storage system controller has received the data.

3. The remote copy system as claimed in claim 1, wherein the acknowledgement back from the second data storage system controller indicates that the data has actually been written to said at least one second data storage device.

4. The remote copy system as claimed in claim 1, wherein the first data storage system returns an i/o completion signal to the host computer, and the data is copied to the second data storage system asynchronously from the time when the first data storage system returns the i/o completion signal to the host computer.

5. The remote copy system as claimed in claim 1, wherein the first data storage system controller returns an i/o completion signal to the host computer after the data has been safely stored in both the first data storage system and in the second data storage system as indicated by the acknowledgement from the second data storage system.

6. The remote copy system as claimed in claim 1, wherein the first data storage system controller includes at least one disk adapter for writing the data from the first cache memory to said at least one first data storage device, and said at least one disk adapter resets the first write pending indicator when it writes the data to said at least one first data storage device.

7. The remote copy system as claimed in claim 1, wherein the second write pending indicator is reset when the second data storage system has written the data to said at least one second data storage device.

8. The remote copy system as claimed in claim 1, wherein the copying of the data from the first data storage system to the second data storage system is controlled independent of and without intervention from any host computer.

9. The remote copy system as claimed in claim 1, wherein the first and second write pending indicators are flags in at least one table of flag bits.

10. The remote copy system as claimed in claim 9, wherein said at least one table of flag bits is maintained by the first data storage system and kept on said at least one first data storage device.

11. The remote copy system as claimed in claim 1, wherein the first and second write pending indicators are flags in a first table of flag bits maintained by the first data storage system and kept on said at least one first data storage device, and the flags are also kept on said at least one second data storage device in a second table of flag bits maintained by the second data storage system.

12. A remote copy system for automatically providing a geographically remote copy of data from a host computer, said system comprising:

a second data storage system geographically removed from the first data storage system, the second data storage system including a second data storage system controller and at least one second data storage device, the second data storage system controller having a second cache memory, the first data storage system controller being coupled to the second data storage system controller for copying the data from the first data storage system controller to the second data storage system controller, the second data storage system controller storing the data in the second cache memory and writing the data into said at least one second data storage device to produce the remote copy of the data from the host computer independent of the host computer;

the first data storage system controller coordinating and controlling the copying of the data to the second data storage system controller wherein, in response to receipt of the data from the host computer, when the data is stored into the first cache memory, a first write pending indicator is set to write the data into said at least one first data storage device, and a second write pending indicator is set to copy the data to the second data storage system controller, the first write pending indicator being reset after the data is written to said at least one first data storage device and the second write pending indicator being reset after receiving an acknowledgement back from the second data storage system controller that the data has at least been received by the second data storage system controller;

wherein the first data storage system returns an i/o completion signal to the host computer, and the data is copied to the second data storage system asynchronously from the time when the first data storage system returns the i/o completion signal to the host computer; and

wherein the copying of the data from the first data storage system to the second data storage system is controlled independent of and without intervention from any host computer.

13. The remote copy system as claimed in claim 12, wherein the acknowledgement back from the second data storage system controller indicates that the data has actually been written to said at least one second data storage device.

14. The remote copy system as claimed in claim 12, wherein the first data storage system controller includes at least one disk adapter for writing the data from the first cache memory to said at least one first data storage device, and said at least one disk adapter resets the first write pending indicator when it writes the data to said at least one first data storage device.

15. The remote copy system as claimed in claim 12, wherein the second write pending indicator is reset when the second data storage system has written the data to said at least one second data storage device.

16. The remote copy system as claimed in claim 12, wherein the first and second write pending indicators are flags in at least one table of flag bits.

17. The remote copy system as claimed in claim 16, wherein said at least one table of flag bits is maintained by the first data storage system and kept on said at least one first data storage device.

18. The remote copy system as claimed in claim 12, wherein the first and second write pending indicators are flags in a first table of flag bits maintained by the first data storage system and kept on said at least one first data storage device, and the flags are also kept on said at least one second data storage device in a second table of flag bits maintained by the second data storage system.

19. A remote copy system for automatically providing a geographically remote copy of data from a host computer, said system comprising:

the first data storage system controller coordinating and controlling the copying of the data to the second data storage system controller wherein, in response to receipt of the data from the host computer, a first write pending indicator is set to write the data into said at least one first data storage device, and a second write pending indicator is set to copy the data to said second data storage system controller, the first write pending indicator being reset after the data is written to said at least one first data storage device and the second write pending indicator being reset after receiving an acknowledgement back from the second data storage system controller that the data has at least been received by the second data storage system controller;

wherein the copying of the data from the first data storage system to the second data storage system is controlled independent of and without intervention from any host computer; and

wherein the first and second write pending indicators are flags in a first table of flag bits maintained by the first data storage system and kept on said at least one first data storage device, and the flags are also kept on said at least one second data storage device in a second table of flag bits maintained by the second data storage system.

20. The remote copy system as claimed in claim 19, wherein the first data storage system controller includes at least one disk adapter for writing the data from the first cache memory to said at least one first data storage device, and said at least one disk adapter resets the first write pending indicator when it writes the data to said at least one first data storage device.

Patent Citations (255)

Patent	Date	Inventor	Cited By
US3588839(A)	1971-06-01	Belady et al.	Applicant
US3623014(A)	1971-11-01	Doelz et al.	Applicant
US3771137(A)	1973-11-01	Barner et al.	Applicant
US3835260(A)	1974-09-01	Prescher et al.	Applicant
US3866182(A)	1975-02-01	Yamada et al.	Applicant
US3936806(A)	1976-02-01	Batcher	Applicant
US4020466(A)	1977-04-01	Cordi et al.	Applicant
US4057849(A)	1977-11-01	Ying et al.	Applicant
US4084231(A)	1978-04-01	Capozzi et al.	Applicant
US4094000(A)	1978-06-01	Brudevold	Applicant
US4124843(A)	1978-11-01	Bramson et al.	Applicant
US4150429(A)	1979-04-01	Ying	Applicant
US4161777(A)	1979-07-01	Behnase et al.	Applicant
US4193113(A)	1980-03-01	Crkowski	Applicant
US4204251(A)	1980-05-01	Brudevold	Applicant
US4249802(A)	1981-02-01	Muchel et al.	Applicant
US4342079(A)	1982-07-01	Stewart et al.	Applicant
US4361855(A)	1982-11-01	Igarashi	Applicant
US4368532(A)	1983-01-01	Imazeki et al.	Applicant
US4384274(A)	1983-05-01	Mao	Applicant
US4396984(A)	1983-08-01	Videki, II	Applicant
US4430727(A)	1984-02-01	Moore et al.	Applicant
US4453215(A)	1984-06-01	Reid	Applicant
US4464713(A)	1984-08-01	Benhase et al.	Applicant
US4523206(A)	1985-06-01	Sasscer	Applicant
US4523275(A)	1985-06-01	Swenson et al.	Applicant
US4530055(A)	1985-07-01	Hamstra et al.	Applicant
US4577272(A)	1986-03-01	Ballew et al.	Applicant
US4594577(A)	1986-06-01	Mao	Applicant
US4598357(A)	1986-07-01	Swenson et al.	Applicant
US4608688(A)	1986-08-01	Hanson et al.	Applicant
US4618827(A)	1986-10-01	Redington et al.	Applicant
US4634100(A)	1987-01-01	Julich et al.	Applicant
US4638424(A)	1987-01-01	Beglin et al.	Applicant
US4686620(A)	1987-08-01	Ng	Applicant
US4698808(A)	1987-10-01	Ishii	Applicant
US4707783(A)	1987-11-01	Lee et al.	Applicant
US4710870(A)	1987-12-01	Blackwell et al.	Applicant
US4726024(A)	1988-02-01	Guziak et al.	Applicant
US4727544(A)	1988-02-01	Brunner et al.	Applicant
US4736407(A)	1988-04-01	Dumas	Applicant
US4751578(A)	1988-06-01	Reiter et al.	Applicant
US4755928(A)	1988-07-01	Johnson et al.	Applicant
US4769764(A)	1988-09-01	Levanon	Applicant
US4771375(A)	1988-09-01	Beglin et al.	Applicant
US4773035(A)	1988-09-01	Lee et al.	Applicant
US4779189(A)	1988-10-01	Legvold et al.	Applicant
US4782486(A)	1988-11-01	Lipcon et al.	Applicant
US4783834(A)	1988-11-01	Anderson et al.	Applicant
US4785472(A)	1988-11-01	Shapiro	Applicant
US4797750(A)	1989-01-01	Karweit	Applicant
US4805106(A)	1989-02-01	Pfeifer	Applicant
US4807186(A)	1989-02-01	Ohnishi et al.	Applicant
US4814592(A)	1989-03-01	Bradt et al.	Applicant
US4823333(A)	1989-04-01	Satoh et al.	Applicant
US4831558(A)	1989-05-01	Shoup et al.	Applicant
US4837680(A)	1989-06-01	Crockett et al.	Applicant
US4841475(A)	1989-06-01	Ishizuka	Applicant
US4849978(A)	1989-07-01	Dishon et al.	Applicant
US4862411(A)	1989-08-01	Dishon et al.	Applicant
US4866611(A)	1989-09-01	Cree et al.	Applicant
US4879718(A)	1989-11-01	Sanner	Applicant
US4916605(A)	1990-04-01	Beardsley et al.	Applicant
US4949187(A)	1990-08-01	Cohen	Applicant
US4958270(A)	1990-09-01	McLaughlin et al.	Applicant
US4959774(A)	1990-09-01	Davis	Applicant
US4960031(A)	1990-10-01	Farrand	Applicant
US4974156(A)	1990-11-01	Harding et al.	Applicant
US4985695(A)	1991-01-01	Wilkinson et al.	Applicant
US5003382(A)	1991-03-01	Omi et al.	Applicant
US5007053(A)	1991-04-01	Iyer et al.	Applicant
US5016876(A)	1991-05-01	Loffredo	Applicant
US5029199(A)	1991-07-01	Jones et al.	Applicant
US5051887(A)	1991-09-01	Berger et al.	Applicant
US5060142(A)	1991-10-01	Menon et al.	Applicant
US5060185(A)	1991-10-01	Naito et al.	Applicant
US5072368(A)	1991-12-01	Foreman et al.	Applicant
US5083271(A)	1992-01-01	Thacher et al.	Applicant
US5087968(A)	1992-02-01	Omi et al.	Applicant
US5088021(A)	1992-02-01	McLaughlin et al.	Applicant
US5089958(A)	1992-02-01	Horton et al.	Applicant
US5093787(A)	1992-03-01	Simmons	Applicant
US5097439(A)	1992-03-01	Patriquin et al.	Applicant
US5099485(A)	1992-03-01	Bruckert et al.	Applicant
US5101492(A)	1992-03-01	Schultz et al.	Applicant
US5109492(A)	1992-04-01	Noguchi et al.	Applicant
US5123099(A)	1992-06-01	Shibata et al.	Applicant
US5127048(A)	1992-06-01	Press et al.	Applicant
US5132787(A)	1992-07-01	Omi et al.	Applicant
US5134711(A)	1992-07-01	Asthana et al.	Applicant
US5140592(A)	1992-08-01	Idleman et al.	Applicant
US5146576(A)	1992-09-01	Beardsley et al.	Applicant
US5146605(A)	1992-09-01	Beukema et al.	Applicant
US5155814(A)	1992-10-01	Beardsley et al.	Applicant
US5155835(A)	1992-10-01	Belsan	Applicant
US5155845(A)	1992-10-01	Beal et al.	Applicant
US5157663(A)	1992-10-01	Major et al.	Applicant
US5157770(A)	1992-10-01	Beardsley et al.	Applicant
US5159671(A)	1992-10-01	Iwami	Applicant
US5170471(A)	1992-12-01	Bonevento et al.	Applicant
US5170480(A)	1992-12-01	Mohan et al.	Applicant
US5175837(A)	1992-12-01	Arnold et al.	Applicant
US5175839(A)	1992-12-01	Ikeda et al.	Applicant
US5185864(A)	1993-02-01	Bonevento et al.	Applicant
US5185884(A)	1993-02-01	Martin et al.	Applicant
US5201053(A)	1993-04-01	Benhase et al.	Applicant
US5202887(A)	1993-04-01	Ueno et al.	Applicant
US5206939(A)	1993-04-01	Yanai et al.	Applicant
US5210865(A)	1993-05-01	Davis et al.	Applicant
US5212772(A)	1993-05-01	Masters	Applicant
US5212784(A)	1993-05-01	Sparks	Applicant
US5235601(A)	1993-08-01	Stallmo et al.	Applicant
US5235687(A)	1993-08-01	Bacot et al.	Applicant
US5235690(A)	1993-08-01	Beardsley et al.	Applicant
US5235692(A)	1993-08-01	Ayres et al.	Applicant
US5239637(A)	1993-08-01	Davis et al.	Applicant
US5239659(A)	1993-08-01	Rudeseal et al.	Applicant
US5257144(A)	1993-10-01	Curasi et al.	Applicant
US5263154(A)	1993-11-01	Eastridge et al.	Applicant
US5269011(A)	1993-12-01	Yanai et al.	Applicant
US5274645(A)	1993-12-01	Idleman et al.	Applicant
US5276867(A)	1994-01-01	Kenley et al.	Applicant
US5276871(A)	1994-01-01	Howarth	Applicant
US5285451(A)	1994-02-01	Henson et al.	Applicant
US5307481(A)	1994-04-01	Shimazaki et al.	Applicant
US5313664(A)	1994-05-01	Sugiyama et al.	Applicant
US5317731(A)	1994-05-01	Dias et al.	Applicant
US5321826(A)	1994-06-01	Ushiro	Applicant
US5335352(A)	1994-08-01	Yanai et al.	Applicant
US5341493(A)	1994-08-01	Yanai et al.	Applicant
US5343477(A)	1994-08-01	Yamada	Applicant
US5357509(A)	1994-10-01	Ohizumi	Applicant
US5367698(A)	1994-11-01	Webber et al.	Applicant
US5375232(A)	1994-12-01	Legvold et al.	Applicant
US5377342(A)	1994-12-01	Sakai et al.	Applicant
US5379412(A)	1995-01-01	Eastridge et al.	Applicant
US5381539(A)	1995-01-01	Yanai et al.	Applicant
US5392390(A)	1995-02-01	Crozier	Applicant
US5404500(A)	1995-04-01	Legvold et al.	Applicant
US5404508(A)	1995-04-01	Konrad et al.	Applicant
US5410667(A)	1995-04-01	Belsan et al.	Examiner
US5412668(A)	1995-05-01	Dewey	Examiner
US5428796(A)	1995-06-01	Iskiyan et al.	Applicant
US5432922(A)	1995-07-01	Polyzois et al.	Applicant
US5434994(A)	1995-07-01	Shaheen et al.	Applicant
US5435004(A)	1995-07-01	Cox et al.	Applicant
US5437022(A)	1995-07-01	Beardsley et al.	Applicant
US5440727(A)	1995-08-01	Bhide et al.	Applicant
US5446872(A)	1995-08-01	Ayres et al.	Applicant
US5450577(A)	1995-09-01	Lai et al.	Applicant
US5459857(A)	1995-10-01	Ludlam et al.	Applicant
US5463752(A)	1995-10-01	Benhase et al.	Applicant
US5469503(A)	1995-11-01	Butensky et al.	Applicant
US5473776(A)	1995-12-01	Nosaki et al.	Applicant
US5479654(A)	1995-12-01	Squibb	Applicant
US5495601(A)	1996-02-01	Narang et al.	Applicant
US5495606(A)	1996-02-01	Borden et al.	Applicant
US5497483(A)	1996-03-01	Beardsley et al.	Applicant
US5502811(A)	1996-03-01	Ripberger	Examiner
US5504888(A)	1996-04-01	Iwamoto et al.	Applicant
US5506986(A)	1996-04-01	Healy	Applicant
US5522031(A)	1996-05-01	Ellis et al.	Applicant
US5526484(A)	1996-06-01	Casper et al.	Applicant
US5535381(A)	1996-07-01	Kopper	Applicant
US5537533(A)	1996-07-01	Staheli et al.	Applicant
US5544345(A)	1996-08-01	Carpenter et al.	Applicant
US5544347(A)	1996-08-01	Yanai et al.	Applicant
US5555371(A)	1996-09-01	Duyanovich et al.	Applicant
US5574950(A)	1996-11-01	Hathorn et al.	Applicant
US5579318(A)	1996-11-01	Reuss et al.	Applicant
US5584039(A)	1996-12-01	Johnson et al.	Applicant
US5592618(A)	1997-01-01	Micka et al.	Applicant
US5592660(A)	1997-01-01	Yokota et al.	Applicant
US5596706(A)	1997-01-01	Shimazaki et al.	Applicant
US5613106(A)	1997-03-01	Thurman et al.	Applicant
US5613155(A)	1997-03-01	Baldiga et al.	Applicant
US5615329(A)	1997-03-01	Kern et al.	Applicant
US5615364(A)	1997-03-01	Marks	Applicant
US5625818(A)	1997-04-01	Zarmer et al.	Applicant
US5633999(A)	1997-05-01	Clowes et al.	Applicant
US5537585(A)	1997-07-01	Blickenstaff et al.	Applicant
US5649089(A)	1997-07-01	Kilner	Applicant
US5649152(A)	1997-07-01	Ohran et al.	Applicant
US5673382(A)	1997-09-01	Cannon et al.	Applicant
US5680580(A)	1997-10-01	Beardsley et al.	Applicant
US5680640(A)	1997-10-01	Ofek et al.	Applicant
US5682396(A)	1997-10-01	Yamamoto et al.	Applicant
US5682513(A)	1997-10-01	Candelaria et al.	Applicant
US5689732(A)	1997-11-01	Kondo	Applicant
US5692155(A)	1997-11-01	Iskiyan et al.	Applicant
US5701429(A)	1997-12-01	Legvold et al.	Applicant
US5721916(A)	1998-02-01	Pardikar	Applicant
US5724500(A)	1998-03-01	Shinmura et al.	Applicant
US5734813(A)	1998-03-01	Yamamoto et al.	Applicant
US5740397(A)	1998-04-01	Levy	Applicant
US5742792(A)	1998-04-01	Yanai et al.	Applicant
US5758149(A)	1998-05-01	Bierma et al.	Applicant
US5764972(A)	1998-06-01	Crouse et al.	Applicant
US5819310(A)	1998-10-01	Vishlitzky et al.	Applicant
US5835954(A)	1998-11-01	Duyanovich et al.	Applicant
US5845295(A)	1998-12-01	Houseman et al.	Applicant
US5852715(A)	1998-12-01	Raz et al.	Applicant
US5889935(A)	1999-03-01	Ofek et al.	Applicant
US5901327(A)	1999-05-01	Ofek	Examiner
US5909483(A)	1999-06-01	Weare et al.	Applicant
US5978565(A)	1999-11-01	Ohran et al.	Applicant
US5987566(A)	1999-11-01	Vishlitzky et al.	Applicant
US6035412(A)	2000-03-01	Tamer et al.	Applicant
US6052797(A)	2000-04-01	Ofek et al.	Applicant
US6044444(A)	2000-05-01	Ofek	Applicant
US6092066(A)	2000-07-01	Ofek	Applicant
US6101497(A)	2000-08-01	Ofek	Applicant
US6108748(A)	2000-08-01	Ofek et al.	Applicant
US6484187(B1)	2002-11-01	Kern et al.	Examiner
US6502205(B1)	2002-12-01	Yanai et al.	Applicant
EP167322	1986-01-01		Applicant
EP239323	1987-09-01		Applicant
EP323123	1988-12-01		Applicant
EP593062(A2)	1994-04-01		Applicant
EP672985(A1)	1995-09-01		Applicant
EP674263(A1)	1995-09-01		Applicant
GB2086625	1992-05-01		Applicant
JP56-153460	1981-11-01		Applicant
JP57-111900	1982-07-01		Applicant
JP62-89150	1987-11-01		Applicant
JP62-274448	1987-11-01		Applicant
JP63-278155	1988-11-01		Applicant
JP1-19437	1989-01-01		Applicant
JP1-19438	1989-01-01		Applicant
JP1-120652	1989-05-01		Applicant
JP2-32418	1990-02-01		Applicant
JP2-32419	1990-02-01		Applicant
JP2-32420	1990-02-01		Applicant
JP2-35537	1990-02-01		Applicant
JP2-37418	1990-02-01		Applicant
JP2-91716	1990-03-01		Applicant
JP2-91717	1990-03-01		Applicant
JP2-93721	1990-04-01		Applicant
JP3-40121	1991-02-01		Applicant
JP3-92942	1991-09-01		Applicant
JP3-93942(U)	1991-09-01		Applicant
JP3-250257	1991-11-01		Applicant
JP3-256143	1991-11-01		Applicant
JP3-256144	1991-11-01		Applicant
JP3-256146	1991-11-01		Applicant
JP5-158631	1993-06-01		Applicant
JP5-233162	1993-09-01		Applicant
JP6-175788	1994-06-01		Applicant
JP7-73078	1995-03-01		Applicant
JP7-191811	1995-07-01		Applicant
JP7-239799	1995-09-01		Applicant
WO94/00816	1994-01-01		Applicant
WO94/25919	1994-11-01		Applicant
WO85/02926	1995-07-01		Applicant
WO95/23376	1995-08-01		Applicant

Non-Patent Literature (147)

D.L. Burkes & R.K. Treiber, “Design Approaches for Real-Time Transaction Processing Remote Site Recovery,” Computer Society International Conference (COMPCON), Spring Meeting, Los Alamitos, Feb. 26-Mar. 2, 1990, No., CONF. 35, Feb. 23, 1990, Institute of Electrical and Electronics Engineers, New York, N.Y., pp. 568-572.Applicant
Supplementary European Search Report for EP 94 91 4223, Jul. 1, 1997. International Search Report for PCT/US/94/04326, Jul. 20, 1994.Applicant
International Search Report for PCT/US/94/04326, Jul. 20, 1994.Applicant
PCT Written Opinion for PCT/US94/04326, Feb. 28, 1995.Applicant
PCT International Preliminary Examination Report for PCT/US94/04326, Jul. 18, 1995.Applicant
SFT Netware 286 Maintenance, #100-313-001, 100/Rev1.00, Novel Incorporated, Provo, Utah, Nov. 1987.Applicant
SFT Netware 286 Installation, #100-312-001, 100/Rev1.00, Novel Incorporated, Provo, Utah, Nov. 1987.Applicant
SFT Netware 286 Installation Supplement, #100-000225-001, 26/Rev1.02, Novel Incorporated, Provo, Utah, Jun. 1986.Applicant
SFT Netware 68 Maintenance, #100-000289-001, 64/Rev1.00, Novel Incorporated, Provo, Utah, Nov. 1986.Applicant
SFT Netware 68 Installation, #100-000317-001, 103/Rev1.00, Novel Incorporated, Provo, Utah, Feb. 1988.Applicant
SFT Netware 868 Installation Supplement, #100-000286-001, 61/Rev1.00, Novel Incorporated, Provo, Utah, Dec. 1986.Applicant
Hank Cote--New Horizons in Accessing Large Amounts of On-Line Data, pp. 71-75, 1982.Applicant
Matt Kramer--Fault-Tolerant LANs Guard Against Malfunction, Data Loss, pp. C26-C35, Sep. 1987.Applicant
Carol Grossman--Planning for 3990 Extended Functions, pp. 245-258, 1989, 30th Annual Guide Conference.Applicant
Bob Buchanan--Administrative Error Causes Most Major System Failures (3 pgs.), Feb. 1988, Government Computer News, V. 17, N. 4, p. 340.Applicant
Virginia Dudek--Planning for Network Disasters (4 pgs.), Jun. 12, 1989, MIS Week, vol. 10, N. 24.Applicant
Jen Bozman--Escon An Aid To Remote Disks (3 pgs.), V. 25, N. 1, p. 29, Jan. 7, 1991.Applicant
Gary A. Boles--A Raid Stack: Micropolis Raidion, Network Computer, Jun. 1992.Applicant
Blaine Homer--Raid Level 5 Protects Your Data With Interleaved Parity, LAN Times, May 25, 1992, vol. 9.Applicant
Michael Caton--Micropolis Array Secures Data, PC Week, 1992.Applicant
RAIDON Fault-Tolerant Disk Arrays Brochure, 1993.Applicant
Storagetek 2Q Earnings Down, Iceberg Ready for Testing by Jim Mallory, Newsbytes, Jul. 15, 1993.Applicant
Network Backup Evolves, by Michael Peterson et al., PC Magazine, vol. 12, No. 16, Sep. 28, 1993, p. 277(18).Applicant
Your Next LAN Storage Could Be a Mainframe, Jeff Moad, Datamination, vol. 39, No. 6, Mar. 15, 1993, p.71.Applicant
Heard Any Good Rumors Lately? (Network Management), By Jill Huntington-Lee, LAN Computing, vol. 5, No. 5, Feb. 1994, p. 22.Applicant
Special Report: The AT&T Worlwide Intelligent Network--Scope, Nature and Management, Edge, vol. 7, No. 224, Nov. 6, 1992, p. 9.Applicant
Software Extends Unix Distributed Computing, by Evan O. Grossman, PC Week, Jun. 5, 1989, p. 35 and p. 40.Applicant
IBM Funds Pack Firm, Electronic News, May 22, 1989, p. 12.Applicant
IBM Plans U.S. Test of File-Transfer, Network World, Sep. 5, 1988, pp. 15, 17.Applicant
IBM Invests In Firm That Offers Unix File-Sharing, Network World, May 22, 1989, p. 4.Applicant
IBM Plans Speedy Nationwide File System, Computer Systems News, Sep. 5, 1988, p. 56.Applicant
Design Alternatives for Disk Duplexing, by Spencer W. Ng, IBM Research Report, Jan. 30, 1987.Applicant
Disk Arm Movement In Anticipation of Future Requests, by Richard P. King, IBM Research Report, Dec. 16, 1987.Applicant
Ubik: Replicated Servers Made Easy, by Michael Leon Kazar, pp. 60-67, 1989.Applicant
Carnegie-Mellon Forges Standard Look For Multivendor Net, Computerworld, Jan. 30, 1989, pp. SR/8-SR/9.Applicant
A Multi-Media Message System for Andrew, USENIX Winter Conference, Feb. 9-12, 1988, pp. 37-42.Applicant
Synchronization and Caching Issues in the Andrew File System, USENIX Winter Conference, Feb. 9-12, 1988, pp. 27-36.Applicant
Comparative Study of Some UNIX Distributed File Systems, EUUG, Sep. 22-24, 1986, pp. 73-82.Applicant
Volumes--The Andrew File System Data Structuring Primitive, EUUG Autumn 1986, Sep. 22-24, 1986, pp. 473-480.Applicant
Unix Plays Role in Corporate Networking, MIS Week, vol. 10, No. 28, Jul. 17, 1989, pp. 22-23.Applicant
Sun's Open System Made by Marketplace, “Unlike Minis, Unix Machines, Pcs and Even VMS Can Be Glued” by NFS, Software Magazine, vol. 9, No. 12, Oct. 1989, pp. 72-75, Cashin, Jerry.Applicant
Protect Your Data! (Database Report), by Michael Liczbanski, Data Based Advisor, vol. 10, No. 5, May 1992, p. 114.Applicant
Network Planning to the Rescue; Network Managers Should Design and Test a Network Recovery Plan That Lets Business Continue Uninterrupted Even If Disaster Strikes, by Ramond W. Rudnitskas et al., Networking Management, vol. 9, No. 11, Oct. 1991, p. 46.Applicant
If LANS Eye Host Status, Quality Today Falls Short, by Barbara Bochenski, Software Magazine, vol. 11, No. 12, Oct. 1991, p. 66.Applicant
Safe and Secure, by Peter Stephenson, LAN Magazine, vol. 6, No. 9, Sep. 1991, p. 34.Applicant
Firing Up Fault Tolerance by Brian O'Connell, DEC Professional, vol. 10, No. 6, Jun. 1991, p. 118.Applicant
A Which Computer? Guide to Backup Systems, by Chris Bidmead, Which Computer?, Sep. 1989, p. 62.Applicant
Optical Disks Compete With Videotape and Magnetic Storage Media, by Henry Urrows et al., Optical Information Systems, vol. 8, No. 3, May-Jun. 1988, p. 101.Applicant
Preventing Disasters: Whipping Up an Emergency Response Plan, Network Computing, Feb. 1992, p. 81.Applicant
Abbey Banking on FDDI, Communications Week International, Mar. 4, 1991, p. 22.Applicant
X.25 Data Networks and IBM: A Troublesome Connection, by Jan Johnson, Computer Decisions, vol. 19, Jan. 12, 1987, p. 16.Applicant
DSC Communications Corp. Debuts NEXOS LAN Product Line at Interface, Demos Enhanced Performance, Fault Tolerance and WAN Connectivity, News Release, Mar. 28, 1988.Applicant
Analysis of Scanning Policies For Reducing Disk Seek Times, by E. G. Coffman, L. A. Klimko and Barbara Ryan-Siam, Journal on Computing, Sep. 1972, vol. 1, No. 3, pp. 269-280.Applicant
Configuring Tandem Disk Subsystems, by Scott Sitler, Tandem Systems Review, Dec. 1986, pp. 80-91.Applicant
Technical Report Investigation of Selected Disk Systems, Oct. 1976, Teledyne Brown Engineering, Huntsville, Alabama (18 pages).Applicant
Universal Server Under Development, MacWEEK, vol. 3, No. 39, Oct. 31, 1989, p. 5.Applicant
Unix Plays Role In Corporate Networking-Vendors Look Unix-Based Network Management Tools as Networking Standards Slowly Evolve, MIS Week, Jul. 17, 1989, pp. 22-23, vol. 10, No. 28.Applicant
The 28 Runners Declared for Open Software Foundations, Distributed Computing Stakes, Computergram International, No. 1301, CGI11909912, Nov. 9, 1989.Applicant
Some Platforms (Theory of Self-Organizing Systems), Release 1.0, vol. 89, No. 6, Jun. 27, 1989, pp. 12-16.Applicant
Self-Organizing Systems (Overview of Detailed Examples of Self-Organizing Systems, Includes related article About the Importance of Self-Organizing Systems), Release 1.0, vol. 89, No. 6, Jun. 27, 1989, pp. 1-9.Applicant
IBM-Funded Startup Developing Unix Add-On, PC Week, vol. 6, No. 22, Jun. 5, 1989, p. 40.Applicant
Uniting File Systems; Experimental Large Scale, Distributed File Systems Are Now Being Created (included related article on the History of the AFS Project), UNIX Review, vol. 7, No. 3, Mar. 1989, pp. 61-70.Applicant
IBM Backs Transarc, Formed to Offer Andrew File System Distributed Unix Database, Computergram International, No. 1180, CGI05190001, May 19, 1989.Applicant
A Comparative Analysis of Disk Scheduling Policies, by Toby J. Reorey and Tad B. Pinerton, Communications of the ACM, Mar. 1972, vol. 15, No. 3, pp. 177-184.Applicant
Disk Scheduling: FCFS vs. SSTF Revisited, by Micha Hofri, Communications of the ACM, Nov. 1980, vol. 23, No. 11, pp. 645-653.Applicant
Using Multiple Replica Classes to Improve Performance in Distributed System, by Peter Triantafillou and David Tayloer, The 11th International Conference on Distributed Computing Systems, May 20-24, 1991, pp. 420-428.Applicant
Government Computer News, Oct. 9, 1987, Richard A. Damca, Microcomputing “Patch Fault Tolerance: A Strong Second Team,” vol. 7, Issue 149 P27(2), Dec. 17, 1990.Applicant
Computer Reseller, Feb. 19, 1990, Joel Shore, Mirrored Servers' a reality, pp. 51, 52, 62.Applicant
Infoworld Articles, Mar. 12, 1990, Vendors Offer Mirroring Solutions P(31).Applicant
Wilkinson, Compact and Novell team for fault tolerance: mirrored servers to cut down on costly downtime, Article MIS Week, vol. 11, Issue 7, Feb. 12, 1990.Applicant
Article PC Week, vol. 4, Issue 37, Sep. 15, 1987, Matt Kramer, Fault-Tolerant LANS Guard Against Malfunction, Data Loss.Applicant
“The DASD Time Bomb,” Datamation, vol. 32, Mar. 1, 1986, P63(4), Alper, Alan.Applicant
Symmetrix Remote Data Facility (SRDF) Product Guide, P/N 200-999-554 Rev A, EMC Corporation, Hopkinton, Mass., Sep. 1994, 105 pp. [EMCP 00003686-3791].Applicant
“Symmetrix Remote Data Facility Data Sheet, Symmetrix-resident Software Feature to extend mirroring capabilities,” EMC Corporation, Hopkinton, Mass., Apr. 1995, 4 pages [EMCP 00010741-1074].Applicant
“When Data is Lost in Minutes, its an Act of God. When Data is Recovered in Minutes, its an Act of EMC.” EMC Corporation, Hopkinton, Mass., 1994, one page [EMCP 00003903].Applicant
“EMC Ships Mainframe Disaster Recovery Solution that Restores Data in Minutes,” News from EMC Corporation, EMC Corporation, Hopkinton, Mass., Oct. 3, 1994, two pages [EMCP 00003921-3922].Applicant
“Asset Protection: Disk-Based Approach Makes Disaster Recovery More Efficient, Ensures Business Continuity,” EMC Corporate Information, EMC Corporation, Hopkinton, Mass., 5 pages [EMCP 00003916-3920].Applicant
“EMC Ships Continuously-Available Disk-Based Disaster Recovery Solution,” News from EMC Corporation, EMC Corporation, Hopkinton, Mass., Oct. 3, 1994, 4 pages [EMCP 00003923-8926].Applicant
“Symmetrix Remote Data Facility: Taking the disaster out of disaster recovery,” Brochure, EMC Corporation, Hopkinton, Mass., Sep. 1994, 8 pages [EMCP 00003908-3915].Applicant
“Symmetrix Remote Data Facility: EMC redefines disaster recovery,” Brochure, EMC Corporation, Hopkinton, Mass., Sep. 1994, 4 pages [EMCP 00003904-3907].Applicant
“EMC Introduces Symmetrix 5500 Continuous Operation Disk Storage for Mission Critical IBM Mainframe Market,” News from EMC Corporation, Hopkinton, Mass., Nov. 10, 1992, 3 pages.Applicant
“MCI Deploys New Fast Data Transfer Technology from EMC,” News from EMC Corporation, Hopkinton, Mass., May 22, 1995, 2 pages [EMCP 00007520-7521].Applicant
“EMC Agreement with Data Switch to Promote Long Distance Disaster Recovery,” News from EMC Corporation, EMC Corporation, Hopkinton, Mass., Nov. 30, 1994, 2 pages [EMCP 00007516-7517].Applicant
“EMC and Comdisco to Benchmark Data Mirroring Capability,” News from EMC Corporation, EMC Corporation, Hopkinton, Mass., Jan. 24, 1995, 2 pages [EMCP 00007518-7519].Applicant
“EMC Ships Mainframe Disaster Recovery Solution that Restores Data in Minutes,” New from EMC Corporation, EMC Corporation, Hopkinton, Mass., Oct. 3, 1994, 2 pages [EMCP 00007514-7515].Applicant
N. S. Prasad, “IBM Mainframes: Architecture and Design,” McGraw-Hill Book Company, New York, N.Y., 1989, pp. 58-73 and 182-196.Applicant
“The IBM 3390 Storage Control Reference,” No. GA32-0099-04, International Business Machines Corporation, Tucson, Arizona, 1991, pp. 1-304.Applicant
Patterson et al., “A Case for Redundant Arrays of Inexpensive Disks (RAID),” Report No. UCB/CSD 87/391, Computer Science Division (EECS), University of California, Berkeley, California, Dec. 1987, pp. 1-24.Applicant
Patterson et al., “Introduction to Redundant Arrays of Inexpensive Disks (RAID),” COMPCON 89 Proceedings, Feb. 27-Mar. 3, 1989, IEEE Computer Society, pp. 112-117.Applicant
Ousterhout et al., “Beating the I/O Bottleneck: A Case for Log-Structured File Systems,” Operating Systems Review, vol. 23, No. 1, ACM Press, Jan., 1989, pp. 11-28.Applicant
Douglis et al., “Log Structured File Systems,” Compcon 89 Proceedings, Feb. 27-Mar. 3, 1989, IEEE Computer Society, pp. 124-129.Applicant
Rosemblum et al., “The Design and Implementation of a Log-Structured File System,” ACM Transactions on Computer Systems, vol. 1, Feb. 1992, pp. 26-52.Applicant
M. Morioka et al., “Design And Evaluation Of The High Performance Multi-Processor Server,” IEEE Transactions, pp. 66-69, 1994.Applicant
A. Reinefeld, “The MOL Project: An Open, Extensible Metacomputer,” IEEE Transactions, pp. 17-31, 1997.Applicant
Robert D. Sloan, “A Practical Implementation Of The Data Base Machine--Teradata DBC/1012,” IEEE Transactions, pp. 320-327, 1992.Applicant
Nancy C. Ramsay, “Integration Of The Optical Storage Processor And The DBC/1012 Data Base Computer,” IEEE Transactions, pp. 94-97, 1990.Applicant
Jim Lyon, “Tandem's Remote Data Facility,” Tandem Computers, Inc., pp. 562-567, Jan. 1990.Applicant
Network backup -INPI Patent No. 93.12771, dated Oct. 21, 1993 “Dispositif Et Procede De Sauvegarde A Distance De Donnees Numeriques,” 15 pages.Applicant
“The Midgets, The Mammoth, And The Mainframes,” Business Week, Jun. 7, 1993, p. 31.Applicant
Complaint --Civil Action No. 00-40188-NMG; EMC Corporation v. StorageApps, Inc., In the United States District Court, District of Massachusetts, Central Section, Oct. 20, 2000.Applicant
First Amended Complaint --Civil Action No. 00-40188-NMG; EMC Corporation v. StorageApps, Inc., In the United States District Court, District of Massachusetts, Central Section, Nov. 9, 2000.Applicant
Answer, Counterclaim and Jury Demand of Defendant StorageApps, Inc. --Civil Action No. 00-41088-NMG; EMC Corporation v. StorageApps, Inc., In the United States District Court, District of Massachusetts, Central Section, Nov. 17, 2000.Applicant
Complaint of EMC Corporation Under Section 337 of the Tariff Act of 130, As Amended, United States International Trade Commission, In the Matter of Certain Data Storage Systems and Components Thereof, Investigation No. 337-TA-_, Apr. 11, 2002.Applicant
Complaint for Patent Infringement, In the United States District Court for the District of Massachusetts (Central Section), Civil Action No. BBO#546481, EMC Corporation v. Hitachi Data Systems Corporation and Hitachi, Ltd., Apr. 11, 2002.Applicant
Notice of Investigation, United States International Trade Commission, Inv. No. 337-TA-471, In the Mater of Certain Data Storage Systems and Components Thereof, May 9, 2002.Applicant
Notice of Investigation, United States International Trade Commission, Inv. No. 337-TA-471, In the Mater of Certain Data Storage Systems and Components Thereof, Federal Register, vol. 67, No. 93, Tuesday, May 14, 2002, pp. 34472-34473.Applicant
Fault Tolerance for LANs and Microcomputers, Atlantic Microsystems, Inc., Salem, NH, 1989 (7 pages).Applicant
IBM 3390 Storage Control Reference, Fifth Edition, Part No. GA32-0099-04, IBM Corporation, Sep. 1991.Applicant
Polyzois and Garcia Molina, “Evaluation of Remote Backup Algorithms for Transaction Processing Systems,” 1992 ACM SIGMOD, pp. 246-255.Applicant
Polyzois and Garcia Molina, “Evaluation of Remote Backup Algorithms for Transaction Processing Systems,” ACM Transactions on Database Systems, vol. 19, No. 3, Sep. 1994, pp. 423-449.Applicant
King and Halim, “Management of a Remote Backup Copy for Disaster Recovery,” ACM Transactions on Database Systems, vol. 16, No. 2, Jun. 1991, pp. 338-368.Applicant
Lyon, J., “Tandem's Remote Data Facility,” IEEE Comp 35th Computer Society Meeting, Spring 1990, pp. 562-567, IEEE Computer Society Press, Los Alamitos, CA..Applicant
Bhide et al., “An Efficient Scheme for Providing High Availability,” 1992 ACM SIGMOND, 1994, pp. 236-245 (also submitted is a four-page Portal.acm.org citation and abstract).Applicant
Gorelik et al., “Sybase Replication Server,” International Conference on Management of Data and Symposium on Principles of Database Management 1994 SIGMOD, p. 469 (also submitted is a two-page portal.acm.org abstract).Applicant
Daniels, et al., “Shared Logging Services for Fault-Tolerant Distributed Computing,” Proceedings of the Fourth Workshop on ACM SIGOPS European Workshop, 1990, pp. 1-4.Applicant
Ohtsuka, S. et al., “M2522/M2531 Optical Disk Library,” Fujitsu-Scientific and Technical Journal, vol. 31, No. 1, Jun. 1995, pp. 65-75.Applicant
Thanhardt, E., and Harano, G., “File Migration in the NCAR Mass Storage System,” Digest of Papers 9th IEEE Symposium on Mass Storage Systems (Editors, Friedman, K., and O'Lear, B.T.), 1988, Storage Systems: Perspectives, Nov. 1988, pp. 114-121 (also submitted is a one-page ieeexplore.ieee.org abstract).Applicant
Hou, R.Y., and Patt, Y.N., “Comparing Rebuild Algorithms for Mirrored and RAID5 Disk Arrays,” Proceedings of the 1993 ACM SIGMOD International Conference on Management of Data and Symposium on Principles of Database Systems, 1993, pp. 317-326 (also submitted is a four-page portal.acm.org abstract).Applicant
Wilkes, J., et al., “The HP AutoRAID Hierarchical Storage Systems,” ACM Transactions on Computer Systems, vol. 14, No. 1, Feb. 1996, pp. 108-136.Applicant
Polyzois, C.A., and Garcia-Molina, H., “Processing of Read-Only Queries at a Remote Backup,” Proceedings of the 13th Symposium on Reliable Distributed Systems, Oct. 25-27, 1994, Dana Point, CA, IEEE Computer Society Press, Los Alamitos, CA, pp. 192-201.Applicant
Schatz, W., “When Data is not Enough,” Computerworld Client/Server Journal, Apr. 1, 1995, pp. 25+ (3 pages downloaded from eLibrary.com).Applicant
Remote Mirroring Technical White Paper, Copyright 1994-2002 Sun Microsystems, published at least as early as May 17, 2002 at sun.com, 25 pages.Applicant
Moad, J., “Will StorageTek's Iceberg Float?”, Datamation, Feb. 1, 1992, pp. 59-60.Applicant
Koop, P., “Replication at Work. (four companies use Oracle and Sybase replication servers to solve business problems),” DBMS, vol. 8, No. 3, p. 54(4), Mar. 1995.Applicant
IBM 3390 Storage Control Reference, No. GA32-009903, Fourth Edition (Dec. 1989), IBM Corporation.Applicant
Double Disk Volume Control Program WDCP/ES, First Edition, Oct., 1997, 6190-3-316-10(E), Hitachi Ltd., Japan.Applicant
P/DAS and Enhancements to the IBM 3990-6 and RAMAC Array Family, First Edition (May 1996), No. SG24-4724-00, IBM Corporation, San Jose, CA.Applicant
Oracle RDMS Database Administrator's Guide, vols. 1 and 2, Part No. 6693-70-0292 Feb. 1992, Oracle Corp., Redwood City, CA.Applicant
Hitachi, Ltd's and Hitachi Data Systems Corporation's Response to the Notice of Investigation and Complaint, Jul. 10, 2002, Investigation No. 337-TA-471, United States International Trade Commission, published at dockets.usitc.gov.Applicant
Respondent's Hitachi, Ltd. and Hitachi Data Systems Corporation's Unopposed Motion for a Modification to the Protective Order, Jul. 11, 2002, Investigation No. 337-TA-417, United States International Trade Commission, published at dockets.usitc.gov.Applicant
United States International Trade Commission, Order No. 5 Modifying Protective Order, Investigation No. 337-TA-471, published at dockets.usitc.gov.Applicant
Hitachi, Ltd. And Hitachi Data Systems Corporation, Submission of Representative Invalidity Charts, Jul. 26, 2002, Investigation No. 337-TA-471, United States International Trade Commission, published at dockets.usitc.gov.Applicant
Hitachi, Ltd's and Hitachi Data Systems Corporation's First Amended Response to the Notice of Investigation and Complaint, Aug. 20, 2002, Investigation No. 337-TA-471, United States International Trade Commission, published at dockets.usitc.gov.Applicant
Lupo, R.V., letter dated Aug. 21, 2002 and regarding typographical errors and enclosed replacement pages for Hitachi, Ltd's and Hitachi Data Systems Corporation's First Amended Response to the Notice of Investigation and Complaint, Aug. 20, 2002, Investigation No. 337-TA-471, United States International Trade Commission, published at dockets.usitc.gov.Applicant
Hitachi, Ltd. And Hitachi Data Systems Corporation, Citations of prior art and other references (5 pages), Investigation No. 337-TA-471, United States International Trade Commission, published at dockets.usitc.gov.Applicant
United States International Trade Commission, Order No. 11 Granting Respondents' Motion to Amend Response and Ordering Submission by Private Parties, Sep. 12, 2002, Investigation No. 337-TA-471, public version published at dockets.usitc.gov.Applicant
Complainant EMC Corporation's Submission in Response to Specific Questions Raised in Order No. 12, Sep. 27, 2002, Investigation No. 337-TA-471, United States International Trade Commission, published at dockets.usitc.gov.Applicant
United States International Trade Commission, Order No. 20 Denying Hitachi's Motion No. 471-16 To Compel, Oct. 25, 2002, Investigation No. 337-TA-471, public version published at dockets.usitc.gov.Applicant
United States International Trade Commission, Order No. 9 Denying Complainant's Motion No. 471-3 To Modify the Protective Order (Order No. 2), Oct. 31, 2002, Investigation No. 337-TA-471, public version published at dockets.usitc.gov.Applicant
United States International Trade Commission, Commission Investigative Staff's Response to Order No. 24, Oct. 31, 2002, Investigation No. 337-TA-471, published at dockets.usitc.gov.Applicant
Complainant EMC Corporation's Submission of Responses to Specific Questions Raised in Order No. 24, Oct. 31, 20002, Investigation No. 337-TA-471, United States International Trade Commission, published at dockets.usitc.gov.Applicant
United States International Trade Commission, Commission Investigative Staff's Response to Order No. 28, Nov. 8, 2002, Investigation No. 337-TA-471, published at dockets.usitc.gov.Applicant
Respondents Hitachi, Ltd and Hitachi Data Corporation's Responses to Order No. 28, Nov. 8, 2002, Investigation No. 337-TA-471, United States International Trade Commission, published at dockets.usitc.gov.Applicant
United States International Trade Commission, Notice of Commission Decision Not To Review and Initial Determination Granting Complainant EMC's Motion To Terminate the Investigation as to Certain Claims and to Amend the Complaint and Notice of Investigation by Adding Two Claims, Federal Register, vol. 87, No. 226, Nov. 22, 2002.Applicant
United States International Trade Commission, Order No. 32 Granting Respondents' Motion No. 471-25 To File A Second Amended Response To The Complaint and Notice of Investigation, Dec. 4, 2002, Investigation No. 337-TA-471, public version published at dockets.usitc.gov.Applicant
United States International Trade Commission, Order No. 44 Requiring Submission From Respondents, Jan. 17, 2003, Investigation No. 337-TA-471, published at dockets.usitc.gov.Applicant
United States International Trade Commission, Order No. 45 Requiring Submission From Respondents, Jan. 21, 2003, Investigation No. 337-TA-471, published at dockets.usitc.gov.Applicant

Abstract