Method and Apparatus for Facilitating Progressive Increase in Allowable Mount/Demounts During Inventory Updates

1. Field of the Invention

This invention relates in general to data storage and processing, and more particularly to the management of inventory updates in a data library.

2. Description of Related Art

The implementation of new technology in magnetic tape products has meant that the density of data written to tape has increased by orders of magnitude in the last ten or fifteen years. The ability to record high density tapes, e.g., ten gigabytes or more on one physical volume, has led to reducing costs in physical tape hardware as well as in handling and management resources.

However, over the past five years, tape data set stacking products, i.e., software solutions to increase tape utilization, have evolved in response to the customer requirement for more efficient ways to manage the information stored on tape. Often a tape library system is provided in conjunction with a library manger. For example, a virtual tape server (VTS) having a tape library has been proposed to achieve increased capacity. In a VTS, the hardware is transparent to the host and the user. The VTS requires little external management except though the library management element of the tape library into which a VTS is integrated.

In a hierarchical storage systems, such as a VTS, intensively used and frequently accessed data is stored in fast but expensive memory. One example of a fast memory is a direct access storage device (DASD). In contrast, less frequently accessed data is stored in less expensive but slower memory. Examples of slower memory are tape drives and disk drive arrays. The goal of the hierarchy is to obtain moderately priced, high-capacity storage while maintaining high-speed access to the stored information.

In the VTS system, a host data interface, a DASD, and a number of tape devices are provided. When the host writes a logical volume, or a file, to the VTS, the data is stored as a file on the DASD. Although the DASD provides quick access to this data, it will eventually reach full capacity and a backup or secondary storage system will be needed. An IBM 3590tape cartridge is one example of a tape device that could be used as a backup or secondary storage system.

When the DASD fills to a predetermined threshold, the logical volume data for a selected logical volume, typically the oldest, is removed from the DASD to free space for more logical volumes. The selected DASD file is then appended onto a tape cartridge, or a physical volume, with the original left on the DASD for possible cache hits. When a DASD file has been appended to a tape cartridge and the original remains on the DASD, the file is "premigrated".

When the host reads a logical volume from the VTS, a cache hit occurs if the logical volume currently resides on the DASD. If the logical volume is not on the DASD, the storage manager determines which of the physical tape volumes contains the logical volume. The corresponding physical volume is then mounted on one of the tape devices, and the data for the logical volume is transferred back to the DASD from the tape.

Tape servers may use an engine to move data between the DASD and tape drives in a virtual tape server (VTS) environment. For example, the IBM Virt Tape Server (VTS) uses the IBM Adstar Distributed Storage Manager (ADSM) as its engine to move data between the DASD and IBM 3590 tape drives on the VTS. In such a system, the VTS uses the a storage manager client on the DASD, e.g., the ADSM Hierarchical Storage Manager (HSM) client, and a distributed storage manager server attached to the tape drives to provide this function. Host systems can also identify volume serial numbers with a category. Then the host systems can request that an entire category be mounted rather than a specific volume serial number. The host will indicate sequential or random order for the mounts.

A tape library dataserver provides automated tape storage for multiple applications such as mid-range computer facilities, LAN servers and archiving applications. To provide high frequency to data, high storage capacity and high performance must be combined. Therefore, knowing the location of data storage media in the tape library is paramount. Typically, the data storage media are bar-coded with a serial number or other identifying marking. Thus, an accessor that is equipped with a bar-code reader can access any cartridge in the library. In addition, the accessor can mount any cartridge located in the library on any library drive. The accessor's management feature permits rapid scanning of all tape cartridge bar-codes.

One function of a tape library dataserver is to provide an update of the locations of data storage media in that library upon resumption of automated operations after the library has been paused and had at least one door opened. Since, while paused, the operator can open any number of doors and move data storage media within the frames of these opened doors, a scan operation must occur to determine which, if any, data storage media have been added, removed, or moved within such frames. Since the location of data storage media within such a library are not known with certainty, any host requests to mount or demount data storage media are held until an inventory update procedure has completed.

However, the inventory update procedure is a time consuming process that currently holds all mount/demount activity in the library while it's in process. Further, the time increases as the length of the library increases. For example, a sixteen frame library takes well over an hour if all doors are being inventoried.

It can be seen that there is a need for a method and apparatus that allows mount/demount activity to occur during an inventory update.

It can also be seen that there is a need for a method and apparatus that allows a corresponding increase in the number of data storage media that are available for mount/demount during the inventory update.

To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for managing inventory updates in a data library.

The present invention solves the above-described problems by providing a method and apparatus that allows mount/demount activity to occur during an inventory update and that allows a corresponding increase in the number of data storage media that are available for mount/demount during the inventory update.

A method in accordance with the principles of the present invention includes the steps of initiating an inventory update for a data storage media library, scanning data storage media in the data storage media library, identifying verified data storage media, receiving a request for moving data storage media between a rack and data storage media drives, determining if the request is for verified data storage media and performing the request when the request is determined to be for verified data storage media

Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the request is requeued when the request is for unverified data storage media Another aspect of the present invention is that the step of identifying verified data storage media further comprises the step of determining whether a frame containing data storage media has had a door to the frame opened and designating the data storage media in a frame having had the door opened as being unverified.

Another aspect of the present invention is that the step of identifying verified data storage media further comprises the step of determining whether a frame containing data storage media has had a door to the frame opened and designating the data storage media in a frame not having had the door opened as being verified.

The invention also includes a data storage media dataserver. The data storage media dataserver includes a data storage media library including data storage media, data storage drives, an accessor for accessing accesses the data storage media from storage slots in the data storage media library and delivering the accessed media to the data storage drives, and a library manager. The library manager initiates an inventory update for the data storage media library, scans data storage media in the data storage media library, identifies verified data storage media, receives a request for moving data storage media between the slots and the data storage drives, determines if the request is for verified data storage media and performs the request when the request is determined to be for verified data storage media.

These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.

Referring now to the drawings in which like reference numbers represent corresponding parts throughout:

FIG. 1 illustrates a virtual tape server system having a tape library dataserver according to the present invention;

FIG. 2 illustrates an automated data storage library;

FIG. 3 illustrates a flow chart of the method for facilitating progressive increase in allowable mount/demounts during inventory updates; and

FIG. 4 is a block diagram that illustrates an exemplary hardware environment for managing inventory updates in a data storage media library according to the present invention.

In the following description of the exemplary embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration the specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized as structural changes may be made without departing from the scope of the present invention.

The present invention provides a method and apparatus that allows mount/demount activity to occur during an inventory update and that allows a corresponding increase in the number of data storage media that are available for mount/demount during the inventory update.

FIG. 1 illustrates a virtual tape server system 100 which may include a tape library dataserver 102 according to the present invention. Those skilled in the art will recognize that the invention is not meant to be limited to a virtual tape server environment, but may be utilized in data library system.

The virtual tape server 100 includes a host computer 110, a distributed storage manager 112, an distributed storage manager server 114, and DASD cache 116. The tape library data server 102 includes a plurality of tape drives 118 forming an automated library 120 and a library manager 122. The virtual tape server 100 also includes an operating system 124 and an automatic storage manager administrator 126 (BATE).

In the VTS 100, intensively used and frequently accessed data is stored in fast but expensive memory, such as direct access storage devices (DASD) 116. In contrast, less frequently accessed data is stored in less expensive but slower memory, such as tape drives 118.

A VTS 100 uses an engine 112 to move data between the DASD 116 and tape drives 118. For example, the IBM Virtual Tape Server (VTS) uses the IBM Adstar Distributed Storage Manager (ADSM) as its engine to move data between the DASD and IBM 3590 tape drives on the VTS. In such a system, the VTS 100 uses the a storage manager client 140, e.g., the ADSM Hierarchical Storage Manager (HSM) client, and a distributed storage manager server 114 attached to the tape drives 118 to provide this function. The library manager 122, via commands from the distributed storage manager server 114, controls an accessor 142 which accesses individual tapes 144.

The distributed storage manager 112 is a client/server hierarchical storage manager 112 that may be used for a broad range of applications. As such, the distributed storage manager 112 often has a downlevel list of which files have a recent copy on one of the tapes 144. Further, the automatic storage manager administrator 126 is provided to link all the VTS code components and external links, e.g., to the library manager 122 and the tapes drives 118.

FIG. 2 illustrates an automated data storage library 200 having an inner "wall" of storage slots 212 and an outer wall of storage slots 214, which store data storage media. Typically, the data storage media are self-contained within a portable container, or cartridge. Examples of such data storage media include magnetic tape cartridges or cassettes, optical disk cartridges of various types, including ROM, WORM and rewritable, and in various formats. For universal reference to any of these types of media, the terms "data storage media" or "media" are used herein.

In addition, the library of the present invention may be a multi-accessor library as illustrated in FIG. 2 having at least two accessors 216 and 217. An accessor is a robotic device which accesses the data storage media from the storage slots and delivers the accessed media to data storage drives 218 and 219 for reading and/or writing data on the accessed media and returns the media to storage slots 212 and 214. A media import/export port or station, 220 is provided for insertion or retrieval of data storage media into or out of the library. The accessors 216 and 217 run on a rail 222 in an aisle between the inner wall of storage slots 212 and the outer wall of storage slots 214.

In the illustrated embodiment, multiple library managers 224 and 225 are provided to manage the positioning and access of the accessors 216 and 217 to transport data storage media between storage slots 212 and 214, import/export port 220 and data storage drives 218 and 219.

An operator input station 228 is provided for allowing an operator to communicate with the automated data storage library. The accessors run on the rails 222 along the library aisle by motors (not shown). An example of an automated data storage library 210 is the IBM 3494 Data Storage Library, which stores magnetic tape cartridges.

Typically, the library manager 224 or 225 comprises a data processor and suitable data memory and data storage capability to control the operation of the library 210. Specifically, the library manager 224 or 225 controls the actions of the robot accessors 216 and 217. The conventional library manager 224 or 225 is interconnected through a provided interface to a host processor (not shown), which provides commands requesting access to particular data storage media or to media in particular storage slots, commands for access to data or to locations on the data storage media and information to be recorded on, or to be read from. Selected data storage media are typically transmitted directly between the drives 218, 219 and the host. The library manager 224 or 225 is typically provided with a database, which includes tables and programs. Examples of library managers 224 and 225 are an IBM personal computer or IBM RS/6000 processor.

Library manager 224 is associated with accessor 216 and library manager 225 is associated with accessor 217. The library manager 224 and associated accessor 216 may be located at one end of the library aisle and designated the "A" library manager and "A" accessor. Similarly, the library manager 225 and associated accessor 217 are at the opposite end of the library aisle and designated the "B" library manager and "B" accessor. The accessor 216 is called the "local" accessor with respect to library manager 224. The accessor 217 is called the "remote" accessor with respect to library manager 224. Similarly, accessor 217 is called the "local" accessor and accessor 216 is called the "remote" accessor with respect to library manager 225.

The present invention may be utilized with a single library manager, or with the illustrated multiple library managers. In accordance with the present invention, one of the accessors is designated as the "active" accessor. In one embodiment, only the active accessor has authorization to be in the aisle and handles all of the operations of the library. This sole authorization may also be called "full aisle mode". In a dual accessor library, in full aisle mode the accessor that is not servicing aisle requests, is the "standby" accessor. If the standby accessor is capable of performing the functions of an active accessor, it is considered to be available in "hot standby mode". If the standby accessor is not capable of performing the functions of an active accessor, it is considered to be "unavailable". In FIG. 2, the standby assessor is moved to the end of the library 244 or 245 and out of the aisle. The ends 244 and 245 of the library are called "service" or "standby" areas.

One function of the tape library dataserver 200 is to provide an update of the locations of data storage media in that library upon resumption of automated operations after the library has been paused and had at least one door opened. Since, while paused, the operator can open any number of doors and move data storage media within the frames of these opened doors, a scan operation must occur to determine which, if any, data storage media have been added, removed, or moved within such frames. Since the location of data storage media within such a library are not known with certainty, any host requests to mount or demount data storage media are held until an inventory update procedure has completed. However, the inventory update procedure is a time consuming process that currently holds all mount/demount activity in the library while it's in process. Further, the time increases as the length of the library increases. In order to mitigate the problem wherein all mount/demount activity is held while the inventory update procedure is in progress, the present invention provides a mechanism wherein some mount/demount activity can occur while the inventory update is in progress, and, as the inventory update progresses, allows a corresponding increase in the number of data storage media that are available for mount/demount during the inventory update.

FIG. 3 illustrates a flow chart 300 of the method for facilitating progressive increase in allowable mount/demounts during inventory updates. First, a mount or demount request is queued 310. Then, the system determines whether commands are being held 312. If commands are not held 314, the system performs the queued mount or demount request 390. If commands are being held 316, the system then determines whether commands are held for inventory update 320. If commands are not being held for inventory update 322, the system requeues the command 360. In the alternative 324, the system determines if the command is a mount 326 or a demount command 328.

If the command is a mount 330, the system determines whether the mount is a mount from category 332. If the mount is a mount from category 334, the system determines the next specific volume in the category 336. Thereafter, the system finds the volume's assigned cell 338.

Once the volume's assigned cell is located, the system determines whether the assigned cell is included in the inventory 340. If the assigned cell is not included in the inventory 342, the system performs the queued mount or demount 390. If the assigned cell is included in the inventory 344, the system determines whether the cartridge has been seen in the assigned cell 346. If the cartridge has been seen in the assigned cell 348, the system performs the queued mount or demount 390. If the cartridge has not been seen in the assigned cell 350, the system determines if a category mount whether there is another cartridge in category that could be mounted 352. If the mount is a category mount 354, the system loops back to determine the next volume in the category 336 if there are more volumes 362. If no more volumes 364, the mount is requeued 360. If the mount is not a category mount 358, the mount is requeued 360.

When the command is determined to be a demount 328, the cell assigned to the volume to be demounted is located 370. Then, the system determines whether the assigned cell is included in the inventory 372. If the assigned cell is not included in the inventory 374, the demount is performed 392. If the assigned cell is included in the inventory 376, the system determines whether the cell has been scanned and determined to be empty 378. If the cell has been scanned and determined to be empty 380, the demount is performed 392. If it is not the case that the cell has been scanned and determined to be empty 382, the demount command is requeued 384.

FIG. 4 is a block diagram 400 that illustrates an exemplary hardware environment for managing inventory updates in a data storage media library according to the present invention. The present invention is typically implemented using a computer 410 comprised of a microprocessor, random access memory (RAM), read-only memory (ROM), and other components. It is envisioned that attached to the computer 410 may be a monitor 412, floppy disk drives 414, and CD-ROM drives 416. Also included in the preferred embodiment may be input devices, for example, a mouse pointing device 420 and a keyboard 422.

The computer 410 operates under the control of an operating system 424, such as the Windows, OS/2, Macintosh, or UNIX operating systems, which is represented in FIG. 4 by the screen display on the monitor 412. The computer 410 executes one or more computer programs 426, which are represented in FIG. 4 by the "windows" displayed on the monitor 412, under the control of the operating system 424. The present invention comprises a data storage media dataserver that is preferably implemented in the operating system 424 and/or computer programs 426.

Generally, the operating system 424 and the computer programs 426 may be tangibly embodied in a computer-readable medium or carrier, e.g. one or more of the fixed and/or removable data storage devices 414 and 416, or other data storage or data communications devices. Both the operating system 424 and the computer programs 426 may be loaded from the data storage devices 414 and 416 into the random access memory of the computer 410 for execution by the microprocessor as discussed above with reference to FIG. 3. Both the operating system 424 and the computer programs 426 comprise instructions which, when read and executed by the microprocessor of the computer 410, causes the computer 410 to perform the steps necessary to execute the steps or elements of the present invention.

Although an exemplary computer system configuration is illustrated in FIG. 4, those skilled in the art will recognize that any number of different configurations performing similar functions may be used in accordance with the present invention.

In summary, all data storage media behind opened doors in the library will be scanned. Any cartridge in a cell within a frame that did not have its door opened, and hence will not be inventoried, will be marked as verified. Any host mount or demount requests will then be examined to see if the request is for a verified cartridge. In the event that it is, the mount/demount will be allowed to proceed, even as the inventory update continues to progress.

For any frames having had a door opened, and hence requiring that they be inventoried, data storage media in the cells of such frames will initially be marked as not verified. This is because they may have been removed from the library or moved within the library. As the inventory update progresses through, columns of cells are scanned and as a result, data storage media within those cells, as identified by their volume serial numbers, become verified and available to satisfy mount/demount requests. So, as the inventory update proceeds towards completion, the number of mount/demount requests that can be satisfied proceeds to the entire set of data storage media.

The foregoing description of the exemplary embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this detailed description, but rather by the claims appended hereto.