Patent Publication Number: US-6715031-B2

Title: System and method for partitioning a storage area network associated data library

Description:
RELATED APPLICATIONS 
     The present invention is related to the following copending and commonly assigned U.S patent application Ser. No. 10/033,009 entitled System and Method for Partitioning a Storage Area Network Associated Data Library Employing Element Addresses, filed Dec. 28, 2001, now pending; Ser. No. 10/032,662 entitled System and Method for Managing Access To Multiple Devices in a Partitioned Data Library, filed Dec. 28, 2001, now pending; Ser. No. 10/032,923 entitled System and Method for Peripheral Device Virtual Functionality Overlay, filed Dec. 28, 2001, now pending; Ser. No. 10/034,518 entitled System and Method for Securing Drive Access to Media Based On Medium Identification Numbers, filed Dec. 28, 2001, now pending; Ser. No. 10/034,588 entitled System and Method for Securing Drive Access to Data Storage Media Based On Medium Identifiers, filed Dec. 28, 2001, now pending; Ser. No. 10/033,010 entitled System and Method for Securing Fiber Channel Drive Access in a Partitioned Data Library, filed Dec. 28, 2001, now pending; Ser. No. 10/033,003 entitled Method for Using Partitioning to Provide Capacity on Demand in Data Libraries, filed Dec. 28, 2001, now pending; Ser. No. 10/034,580 entitled System and Method for Intermediating Communication with a Moveable Media Library Utilizing a Plurality of Partitions, filed Dec. 28, 2001, now allowed; and Ser. No. 10/034,083, entitled System and Method for Managing a Moveable Media Library with Library Partitions, filed Dec. 28, 2001, now pending; the disclosures of which are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention is generally related to data storage and specifically to a system and method for partitioning a storage area network associated data library. 
     BACKGROUND 
     One of the most attractive aspects of a storage area network (SAN) is that network connectivity enables a company to efficiently use storage by sharing storage capacity among a number of servers. This may be implemented using a large number of small capacity storage devices. However, unless sufficiently robust management software is employed, such use of small capacity devices in a SAN may result in significant management overhead. 
     Most users prefer to install large capacity storage device(s) and partition the device(s), assigning each partition to a different server. For example, existing firmware for enterprise level disk arrays allow users to define multiple redundant array of independent disks (RAID) sets, where each RAID set appears as a different logical unit number (LUN). Each one of these LUNs may be dedicated to a different server. However, to-date special hardware, as described below, or special backup software has been used to implement partitioning. 
     An existing hardware-based partitioning scheme for existing libraries is known as shared library services. This implementation requires at least one bridge, sometimes referred to as a quad interface processor, to be placed between the drives and the library controller. The host side of each quad interface processor consists of two small computer systems interface (SCSI) buses, and the quad interface processor may show a single virtual library controller, with its own SCSI ID, on each SCSI bus. Thus there may be one virtual library per host SCSI bus, containing the virtual library controller and the drives in that partition. Each partition of such an existing library may have slots added in increments and drives may be added individually or in pairs. Each internal SCSI bus in this existing partitioning scheme may accommodate up to two drives; drives on the same bus must be in the same partition. 
     Such an existing hardware-based library partitioning scheme may use switches to provide secure partitioning. Existing quad interface processor bridges employ a SCSI target ID for each partition. Each SCSI ID may have a separate SCSI/fiber channel (FC) bridge associated with it. Other existing libraries do not provide secure partitioning. 
     Existing software-based partitioning solutions typically employ a host system that restricts access to portions of a tape library. The host restrictions are implemented by a mediating (software) process on a host system to enforce partition restrictions. However, this approach is problematic. Specifically, the approach is undesirable if the tape library is utilized in a storage service provider (SSP) environment. In SSP environments, the tape library and the host systems belong to different entities (e.g., the SSP and the customers). Placement of software mediating processes on host systems is unattractive, because it increases the burden on the customers to make use of the storage service. Also, corporate environments impose relatively long qualification cycles for new host system software. New software is typically only introduced in such environments once every six to eight months due to qualification cycles. Moreover, many customers are unwilling to allow other parties to place software on their host systems. Additionally, the software mediating process approach is typically incompatible with existing data back-up utilities, i.e., the software mediating process approach requires the use of specialized data back-up applications. Hence, users are effectively denied the ability to run desired backup software. 
     SUMMARY OF THE INVENTION 
     A storage area network associated data library partitioning system comprises a plurality of storage element slots adapted to store data storage media, at least one set of at least one of the slots is assigned to one partition of a plurality of partitions, a plurality of data transfer elements that are adapted to receive the media and transfer data to and from the media, each of at least one set of at least one of the data transfer elements is assigned to one of the partitions, and a library controller that assigns a different logical element designation to a virtual controller for each of the partitions, the virtual controllers directing movement of the media to and from one of the set of slots assigned to a same of the partitions. 
     A method in accordance with the present invention for partitioning a storage area network associated data library comprises assigning a different logical element designation to each of a plurality of library partitions, establishing the partitions in the data library, each of the partitions comprising at least one storage element slot and at least one data transfer element, each of the slots adapted to store media, and each of the data transfer elements adapted to receive the media and transfer data to and from the media, and controlling movement of the media to and from the slots assigned to a same partition. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic illustration of a SAN operating consistent with the teachings of the present invention; 
     FIG. 2 is a diagrammatic illustration of an example of a data library employing an embodiment of the data library partitioning system and method of the present system; 
     FIG. 3 is a flow chart of creation of a partition in accordance with the inventive partitioning method of the present invention; 
     FIG. 4 is a flow chart of deletion of a partition in accordance with the inventive partitioning method of the present invention; 
     FIG. 5 is a flow chart of enlargement of a partition in accordance with the inventive partitioning method of the present invention; 
     FIG. 6 is a flow chart of reduction of a partition in accordance with the inventive partitioning method of the present invention; 
     FIG. 7 is a flow chart showing an alteration of the security configuration of a partition in accordance with the inventive partitioning method of the present invention; 
     FIGS. 8A through 8D are diagrammatic illustrations of an exemplary, data tape library partitioned consistent with the teachings of the present invention by the present system, under a flexibility embodiment with the partitions being redefined between FIGS. 8A through 8D; and 
     FIGS. 9A through 9D are diagrammatic illustrations of an exemplary, data tape library partitioned by the present system, under a compatibility embodiment with the partitions being redefined between FIGS.  9 A through  9 D. 
    
    
     DETAILED DESCRIPTION 
     The present data library partitioning system and method for storage area networks enables a data library to be shared among a number of servers and/or RAID partitions by partitioning the library. Under the present system and method a subset of the library drives and media slots are secured or reserved for the exclusive use of a specific server. The presence of, as well as access to, a partition may also be secured. A library partition in accordance with the present invention may identify itself and present identical resources, such as drive(s), storage element(s) and/or transport(s), as an existing tape library model so that existing software may recognize the library type. 
     The present system and method eliminates the need for special bridges such as the aforementioned quad interface processors. Thereby, the present system and method also eliminates the need to have all drives in a partition on a same SCSI bus to a host, thereby avoiding resulting potential bottlenecks. Instead standard existing library architectures may be used by the present invention, with drives allowed to employ existing SCSI buses. In order to implement multiple virtual controllers with each virtual controller assigned to a separate partition, the controller preferably assigns a different SCSI LUN or similar logical element designation, preferably under the controller&#39;s SCSI ID, to a virtual controller for each partition. Partitions may be secured in a FC-SAN environment by only allowing access to specified hosts, keyed on unique host device identifiers such as world wide names (WWN), without requiring external switches to implement switch zoning to secure partitions. Integrated configuration of all major components involved in secure partitioning, including but not limited to bridges, library controller and drives, by the present library management system and method provide a simple point-and-click setup process. This greatly reduces management overhead and margin for error compared to existing libraries employing multiple bridges and FC switch zoning, where each component has to be separately set up. 
     The present SAN partitioning system and method is preferably adapted for use with an internet small computer systems interface (iSCSI) associated library as well an FC attached library or SCSI-based library. Unique host device identifiers for security in an iSCSI environment may be iSCSI names or other unique identifiers such as Ethernet addresses. 
     Turning to FIG. 1, SAN  100  is shown. By way of example, first and second customer servers  101  and  102  are connected to SAN  100  via FC switch  103 . RAID  104  may be partitioned assigning first partition  105  to server  101  and second partition  106  to server  102  using existing LUN-based RAID partitioning methods. Zero downtime backups (ZDBs) may be performed of the data each server has on the RAID to tape library  108 , via ZDB interconnectivity  107  between RAID  104  and tape library  108 . Such ZDBs may employ data-mover firmware embodied in RAID  104  or other SAN elements. ZDBs are preferably carried out without impinging on processor operations or local area network (LAN) capacity of servers  101  and  102 . Tape library  108  is preferably partitioned employing an embodiment of the present system and method to ensure that data for server  101  is maintained in partition  109  separate from data for server  102 , and that the data of server  102  is maintained in partition  110  separate from data for server  101 . Such partitioning ensures that the servers may not access each other&#39;s data even though both servers&#39; data is maintained in the same physical library. 
     Data tape library  200  employing a preferred embodiment of the present system and method is illustrated in FIG. 2 as an example of a library that may be employed as library  108  of FIG.  1 . However, other library designs and/or capacities may embody the present system and method. Exemplar data tape library  200  has four data transfer elements in the form of tape drives  201 - 204 , forty media storage element slots  205  that are shown organized into four trays  206 - 209  of ten slots  205  each, two FC-to-SCSI bridges  210  and  211 , a library management interface card or remote management card (RMC)  212  and library controller  213 . Tape drives  201 - 204 , FC-to-SCSI bridges  210  and  211 , RMC  212  and library controller  213  preferably communicate with each other using an inter-integrated circuit (I 2 C) serial management bus and/or automated control interface (ACI)  214  or the like. Any of tape drives  201 - 204  may be SCSI based devices or FC tape drives that may employ cartridge memory (CM) reading functionality. 
     For partitions according to the present system and method, library media slots  205  and tape-drives  201 - 204  should be assigned to each partition, and a virtual library controller should be addressable with respect to each partition. The slots may be assigned by trays or individually. The example partitioning shown in FIG. 2 is indicated by boxes  215 ,  216  and  217 . As illustrated, LUN 0  corresponds to partition  215 , LUN 1  corresponds to partition  216  and LUN 2  corresponds to partition  217 . Finally, import/export elements or mailslots may be assigned to each partition or configured for use by the entire library. Preferably, easily-accessible media storage slots may be configured as mailslots by the present invention. 
     In the present library partitioning implementation, library partitioning is preferably configured out-of-band either on the library&#39;s front panel management interface or via secure RMC  212  over associated LAN  218  or the like. This helps ensure controlled access security of the partitioning process by, for example, limiting access to users with access to LAN  218  or physical access to the front panel of library  200 . Alternatively, the present partitioning system and method may be configured over a secured in-band connection. Over out-of-band LAN  218 , configuration may either be carried out via a web browser interface or via a network management protocol interface. By default, data library  200  will preferably contain one unsecured partition preferably labeled as partition  0  that contains a standard configuration of library data transfer elements (drives)  201 - 204 , library storage elements (slots)  205  including import/export elements (mailslots), and data movers associated with library  200 . 
     For the present partitioning system and method to be transparent to a user server, the library robotic arm used to move media from slots to drives may be shared among user servers. However, it should appear to each server that it is the owner of the arm. Mailslots are also shared resources that need to be virtualized or replicated by the partitioning system. Therefore, import/export elements should either be assigned to partitions similar to the storage elements or ownership of the import/export elements should be virtualized. 
     Each created partition preferably has one mailslot initially, except as discussed below when emulating a library without a mailslot. Preferably, the mailslot configuration of the partition may be altered once the partition is created, using the standard mechanisms/interfaces provided by the tape library. However, mailslots should be configured on a per-partition basis. If a tape drive or mailslot in a partition is loaded with a tape, a request to alter the configuration of the partition associated with the tape, tape drive and/or mailslot should be denied until the mailslot is cleared. 
     Most libraries have a single library controller addressed via a single SCSI ID. To eliminate the need to have a number of cooperating controllers as in existing partitioning systems, the SCSI LUN scheme defined in the SCSI standard is preferably used by the present system and method to enable controller  213  to present multiple instances of itself. Preferably, controller  213  partitions the storage slots and import/exports slots as requested via RMC  212 . For example, a first instance of the library controller may be presented on LUN 0  for partition  215 ; a second instance might be presented on LUN 1  for partition  216 ; and a third instance on LUN 2  for partition  217 . Although only one physical controller  213  is needed on the SCSI bus, the controller firmware may be called upon to deal with a command active on each individual LUN (i.e., properly support disconnects), and correctly maintain the current active state for each LUN (e.g., response to test unit ready and request sense, mode pages, log pages, etc). 
     Preferably, library partitioning is configured out-of band, for example over LAN  218  through RMC  212 , via a secure web browser interface or the like. Preferably, LAN  218  is an Ethernet network or the like dedicated to management of SAN resources. Alternatively, configuration of partitions may be programmatically carried out via a network management protocol. Preferably, RMC  212  communicates with library controller  213 , FC-to-SCSI bridges  210 ,  211  and/or tape drives  201 - 204  to communicate configuration information to implement the selected partitioning. Preferably, RMC  212  will also show diagrammatically, via a web browser interface, or schematically, via a network management protocol interface, how library  200  is partitioned. 
     By way of example, firmware of FC-to-SCSI bridges  210  and  211  should only allow commands from valid hosts, which may be based on a unique host identifier such as WWN, to be passed to controller  213  and drives in library  200 . In addition, bridges  210  and  211  should only show components, tape drives  201 - 204  and a library controller instance that are members of the partition or partitions the host has been allowed to access. An appropriate LUN mapping scheme should be used to avoid gaps in the LUN numbering shown behind the bridge FC arbitrated loop physical address (ALPA). Finally, any data-movers associated with the bridge should be subject to per-host security preventing data exchange via data-mover system  107  or the like to an inappropriate host. Data mover security may also be based upon a unique host identifier such as WWN. 
     RMC  212  will preferably process requests received out of band via the web browser interface or network management protocol interface to alter configuration of a specified partition, one at a time. The authority of a requester is ensured by controlled access security incorporated into the present system and method. For example, LAN  218  is preferably dedicated to managing SAN resources and is preferably not available to outside users; the web browser user interface preferably requires a secure log-on; and the network management protocol interface is also preferably protected by similar password authentication. Preferably, at least four different types of requests may be processed, as illustrated in FIGS. 3-6. 
     Turning to FIG. 3, create partition request  300  initiated at box  301  preferably contains, or the user is prompted to provide, the first data transfer element address and the number of data transfer elements for the new partition, as well as the first slot address and the number of slots for the new partition, box  302 . As part of create partition process  300 , the user is provided a default choice of making the partition unsecured or given the option of securing the partition at  303 . If the user chooses to secure the partition at box  304 , the user enters a list of a unique host identifiers, such as WWNs, for hosts allowed to access the partition. At box  305  the new partition should be assigned the lowest partition number available and slot and transfer elements requested at box  302 . All elements for a new partition should be disabled prior to selection and selected elements should conform to configuration rules for the overall partitioning scheme the library is operating under by being contiguous. 
     Delete partition request  400  is depicted in FIG.  4 . Preferably initiation of a delete partition request at box  401  contains the number of the partition or the user is prompted to provide the partition number at box  402 . As a result of the delete command, all elements in the partition will preferably be disabled at box  403 . 
     Enlarge partition request  500 , as shown in FIG. 5, preferably identifies the partition being enlarged, contains the first data transfer element address to be added, indicates the number of data transfer elements to be added, identifies the first slot address to be added and specifies the number of slots to be added. This information may be provided when the user initiates enlarge request  500  at box  501  or the user may be prompted to provide the information at box  502 . The elements added at box  503  should be disabled prior to selection and selection of elements should conform to the configuration rules of the partitioning scheme the library is operating under by being contiguous with existing elements of the partition. 
     In FIG. 6, shrink partition request  600  preferably identifies, at box  601 , or prompts the user to provide at box  602 , the partition being reduced. Request  601  or prompt  602  preferably includes first data transfer element address to be removed, enumerates the number of data transfer elements to be removed, indicates the first slot address of the slots to be removed and specifies the number of slots to be removed. The elements selected for removal at box  603  should conform to the configuration rules of the partitioning scheme the library is operating under by being contiguous with each other and the existing partition. Enlarge and shrink partition requests  500  and  600 , respectively, may only be valid for a flexibility-oriented partition embodiment as discussed in greater detail below. 
     Turning to FIG. 7, if the user subsequently selects to alter the security configuration of a partition, process  700  is employed. Upon evoking a security alteration request at box  701 , the user may be presented with a default choice of making the partition unsecured at  704 . The default choice at  704  is preferably unsecured. Selection of unsecured at  704  results in security for the partition being set to unsecured at box  705 . If the user chooses to secure the partition at  704 , then the user is prompted to enter a list of WWNs or other applicable unique host device identifiers to be allowed access to the identified partition at box  706 . 
     The RMC is preferably responsible for maintaining overall coordination regarding how the library partitioning is configured. Accordingly, the RMC of the preferred embodiment communicates with the library controller to direct configuration of the library controller to implement the selected partitioning. The RMC may also communicate with any FC-to-SCSI bridges and FC tape drives in the library to configure security. The RMC will preferably show diagrammatically via its web browser interface, on the library front panel or schematically via a network management protocol interface, how its library is partitioned. Preferably, a user may configure the partitioning by selection of elements on the diagram and selecting a type of request, such as create partition  300 , delete partition  400 , enlarge partition  500 , shrink partition  600 , or change security configuration of partition  700 . 
     If an FC-to-SCSI bridge supports data-mover LUNs then, according to a preferred embodiment, the data-mover FC LUNs may also be added/removed to and from partitions and viewed as part of the partition configuration via the RMC. The security applied to a data-mover LUN will preferably be the security applied to the partition of which it is a member. Thus, WWN-based security may be employed to control access to data movers in the present system and method. Removal of a data mover from a partition results in the data-mover being disabled, which means it will not accept requests from any host. If these data-movers are embodied in (a) FC-to-SCSI bridge(s), the data-mover LUNs may not be listed as elements by the library controller as such data movers may only exist in the FC-to-SCSI bridge. Data-mover functionality may also be incorporated into existing FC tape drives that are a part of the data library. 
     Preferably, library partitioning will be persistent between power-cycles and will not require a power cycle for partitioning alterations to take effect. Preferably, the RMC will detect a firmware update to the library controller, and accordingly reconfigure the partitioning in the library controller. 
     Media movement options, such as maintenance or inventory-related media movement, available on the RMC web browser page or front panel preferably limits media movement to within partitions. In other words, media will preferably only be moved between tape drives, storage slots and mailslots within the same partition. This may also include the use of cleaning cartridges. This limitation may be implemented by requiring the user to select a partition first before selecting the type of operation, and the operation should limit choices to drives and slots in that partition. Library diagnostics should ensure, that during diagnosis, media is never moved out of assigned partitions and that media is maintained in the slots or drives of its assigned partition. Inventory checking and/or door locking and unlocking functions may preferably be allowed through at least one selected partition for the entire library and for partitions on a per partition basis. 
     By default the library preferably contains one partition, the entire library, with no security applied to facilitate setup of partitions as necessary. Preferably, a user may alter partitioning using one of a number of embodiments. Two such embodiments are presented below. A library will preferably be configured to only use one partition embodiment at a time. To change the partition embodiment used, all partitions should be deleted, resulting in all elements being disabled. Of possible partitioning embodiments, one is optimized for flexibility and another for compatibility with existing backup software. 
     FIGS. 8A-8D show examples of valid assignments of drive(s) and slots, by trays, during stages of reconfiguration of partitioning, consistent with valid partitioning under a flexibility embodiment  800 . Preferably, a flexibility-oriented embodiment  800  allows partitions  801 ,  802  and  803  in the library to contain multiples of slots or a number of trays  804  through  817 , each made up of a number of slots. All of the slots selected are preferably in a contiguous sequence of storage element numbers to facilitate slot renumbering under a specific LUN. Preferably, in each partition any import/export elements are made up of the highest numbered storage elements in the partition. Preferably, at least one drive  818  through  823  is included in a partition, allowing a partition to operate independent of other partitions. Drives  818  through  823  in partitions  801  through  803  are preferably in a contiguous sequence of data transfer element numbers. A library controller inquiry string for each active partition under the flexibility embodiment is preferably unique. The inquiry string is preferably based on the number of slots and drives in the partition, similar to inquiry strings for existing libraries. 
     Generally, all actions that may be performed on partitions under the present system and method may be performed on partitions  801 - 803  under the flexibility-oriented embodiment. As discussed earlier in reference to FIG. 4, delete partition request results in slots, or trays, and data transfer elements in the partition being disabled. Thereby, the slots and data transfer elements should be designated as not belonging to any secured or unsecured partition. A create partition request as discussed in reference to FIG. 3 may be carried out using selected, previously disabled, slots and data transfer elements. A remove or shrink request of FIG. 6 is preferably permitted for selected slots, in blocks of slots or a tray at a time and by data transfer elements from a partition. The selected tray of slots is preferably either at the start or the end of the list of slots in the partition to ensure that the partition is comprised of contiguous slots. Similarly, data transfer elements to be removed preferably are either at the end or the start of the list of data transfer elements in the partition to ensure that the partition is comprised of contiguously numbered data transfer elements. These slots or trays and data transfer elements should then be disabled, not belonging to any secured or unsecured partition. Add requests, consistent with the enlarge request of FIG. 5, deal in selected disabled blocks of slots or individual trays and data transfer elements for a partition. Selected additional trays of slots are preferably either at the start or the end of the list of slots in that partition to ensure that the partition is comprised of contiguous slots. Similarly, data transfer elements added are preferably either at the end or the start of the list of data transfer elements in the partition to ensure that the partition is comprised of contiguously numbered data transfer elements. Therefore, moving slots or data transfer elements from one partition to another may be accomplished in a two-stage process. First the slots and/or data transfer elements are removed from a partition disabling the slots and/or data transfer elements. Then the slots and/or data transfer elements are added to the second partition. 
     In FIG. 8A a six drive, fourteen tray library employing flexibility embodiment  800  is divided into partitions  801 ,  802  and  803 . First partition  801  has two drives  818  and  819  and four trays  804  through  807 , for forty slots. Second partition  802  has two drives  820  and  821  and four trays  808  through  811 , for forty slots. Third partition  803  has two drives  822  and  823  and two trays  812  and  813 , for twenty slots. Trays  814  through  817  are disabled and unassigned in FIG. 8A 
     A set of thirty slots, trays  805 ,  806  and  807  and drive  819  have been disabled between FIGS. 8A and 8B. This is preferably carried out using a remove request designating partition  801  and the slots of trays  805  through  807  and drive  819 . 
     In FIG. 8C, the disabled drive  819  and slots of trays  805  through  807  are added to partition  802  using an add request designating the slots of trays  805  through  807  and drive  819 . This addition is permitted, according to a preferred embodiment, as the slots are disabled and are contiguous with existing partition  802  slots of tray  808 . Similarly, drive  819  was disabled and contiguous with drive  820  of partition  802 . 
     In FIG. 8D, the previously unassigned and therefore disabled slots of trays  814  through  817  are added to partition  803  using an add request. The slots of trays  814  through  817  are contiguous with existing slots of tray  813  of partition  803 . Therefore, this addition is also permissible according to a preferred embodiment. 
     A flexibility-oriented partition may be configured using methods provided by the library to have a number of import/export elements. Generally, a partition may have zero, one, five or ten import/export elements. The import/export elements will preferably be comprised of the highest numbered slots of the last tray in a partition and will preferably be reassigned as appropriate as a partition is resized. Therefore, in FIGS. 8A through 8D, the mailslot(s) assigned for partition  801  is preferably the highest number slot(s) of tray  807  in FIG.  8 A. Then the highest number slot(s) of tray  804  is reassigned as mailslot(s) for partition  801  in FIG.  8 B. The mailslot for partition  802  preferably remains the highest number slot of tray  811  throughout FIGS. 8A through 8D. The mailslot(s) for partition  803  moves from the highest number slot(s) of tray  813  in FIGS. 8A through 8C to the highest number slot(s) of tray  817  in FIGS.  8 D. 
     Turning to FIGS. 9A through 9D, compatibility-oriented embodiment  900  provides simplicity and backup software compatibility. Partitions  901 ,  902 ,  903 ,  924  and  925  in a library under a compatibility-oriented embodiment should be equivalent to or emulate existing, or otherwise known data library models. For example, a one drive-nine slot (1/9) library may be emulated using one drive  918  and one tray  904  of slots on one level of a library to provide partition  901  as illustrated in FIG.  9 A. In such a 1/9 partition configuration, one slot is not used and is disabled. Preferably, no mailslots are allowed in such a 1/9 partition as no mailslots are present in existing 1/9 libraries. Two 1/9 partitions  901  and  902  may share a level in the illustrated example library shown in FIG.  9 A. Preferably, a 2/20 partition, such as partition  924 , takes up all of one level and preferably is not split among levels, as shown in FIGS. 9C and 9D, to facilitate emulation of existing library models. 2/20 partition  924  contains two drives  920  and  921  and twenty slots or two trays  906  and  907 , from which zero, one, five or ten mailslots may be defined. Four drive and forty slot, 4/40 partition  903  preferably takes up all of two levels and preferably is not split among levels as shown in FIG.  9 A. Zero, one, five or ten of the slots may be defined as mailslots for partition  903 . Preferably, a 6/60 partition would contain six drives, such as drives  918  through  923 , and sixty slots or six trays, such as trays  904  through  909 . A 6/60 compatible partition would preferably take up all of three levels of the library and preferably not be split among levels. Zero, one, five or ten of the sixty slots may be defined as mailslots in a 6/60 emulated library. A 6/140 partition containing six drives  918  through  923  and one hundred forty slots in fourteen trays  904  through  917  taking up all of the seven illustrated levels such a 6/140 partitioning of an entire library may be desirable to apply security to the partition as discussed above. Zero, one, five or ten mailslots may be defined from the slots of the 6/140 library. 
     In existing tape libraries that do not have drives for each level, partitioning using a compatibility-oriented embodiment may call for trays or slots lacking associated drives to be disabled. Therefore, if a 6/140 data tape library, as illustrated in FIGS. 9A through 9D is partitioned other than as a standard 6/140 configuration (i.e., the library contains one or more 1/9, 2/20, 4/40 or 6/60 partitions) trays  910  through  917  of the top four levels of such an existing 6/140 library may be disabled as shown. This preserves the aforementioned emulation, as existing 1/9, 2/20, 4/40, 6/60 libraries being emulated by the compatibility embodiment do not support slots or trays without drives on a level. In the compatibility embodiment, the library controller inquiry string for each active partition type should be the standard inquiry string for the corresponding existing library type or model. 
     The actions that may be performed on partitions in the compatibility-oriented embodiment  900  may be limited. In compatibility-oriented embodiment  900 , partitions are preferably deleted and created as a whole. For example, to resize a 1/9 partition to be part of a 2/20 partition, the 1/9 partition should be deleted, disabling the elements, and the 2/20 partition then created from disabled contiguous elements preferably on the same level. For a delete partition request, as discussed in relation to FIG. 4 above, the slots and data transfer elements in the partition are disabled; and therefore, do not belong to a secured or unsecured partition. A user may create a partition consistent with the process illustrated in FIG. 3 from valid selected disabled slots and data transfer elements. For illustrated compatibility embodiment  900  a valid selection is comprised of a contiguous set of ten (nine active), twenty, forty, sixty or one hundred forty slots and a corresponding contiguous set of one, two, four or six drives. In this embodiment, if a partition with more than ten slots is selected then the partition preferably fully occupies each associated layer in the library to facilitate emulation of existing library models. Ten, twenty, forty or sixty slot partitions should also contain the tape drive associated with each set of ten slots sets of trays. A one hundred forty slot partition of an existing 6/140 library should contain the six drives in the lower three layers of the library. A partition may be configured as allowed by the library to have zero, one, five or ten import/export elements. Preferably, the mailslots will be at the front of the last tray in the partition, the highest numbered slots in the partition, and will be reassigned as appropriate if the partition is resized. 
     In FIG. 9A, a six drive, fourteen tray library is divided into partitions  901 ,  902  and  903 . First and second partitions  901  have one drive  918  and  919 , respectively, and one tray each  904  and  905 , respectively. Partition  903  emulates a 4/40 library and has four drives  920  through  923  and four trays  906  through  909  for forty slots. 
     Partitions  902  and  903  are deleted between FIGS. 9A and 9B. Therefore, trays  905  through  909  and drives  919  through  923  are shown as unassigned in FIG.  9 B. 
     2/20 emulated library  924  is created between FIG. 9B and 9C. Contiguous trays  906  and  907  and drives  920  and  921  on the same level are used to create 2/20 partition  924 . Similarly, 2/20 library emulation partition  925  of FIG. 9D is created from co-level, contiguous, unassigned trays  908  and  909  and the same level drives  922  and  923 . Tray  905  and drive  919  remain unassigned in FIG.  9 D. 
     To provide security in a fibre channel environment, the user may also configure which hosts have access to the resources such as tape drives, library controller and media in each partition. This may be carried out via a web browser interface or via a network management protocol interface. The user may select an active partition and configure the partition to either be unsecured, allowing all hosts access, or restrict access to a list of host WWNs. When a partition is created using the present system and method, by default its security level is set to unsecured. Similarly, the default partitioning of the entire library as partition  0  applies a default security setting of unsecured to partition  0 . To prevent all hosts from accessing a partition, the partition may be configured with an empty list of WWNs. Also, access by all hosts to disabled resources not in an active partition is preferably restricted. 
     If a user modifies a partition&#39;s device resources via the library web browser management interface (e.g., adds a device or removes a device), the library management firmware preferably updates the security information on all of the FC-to-SCSI bridges that attach to that partition&#39;s device resources, and any native FC drives in the library. This is preferably carried out by sending a security configuration request to each of the FC-to-SCSI bridges and FC tape drives, updating the security on all of the devices in that partition. Thereby, the library management firmware should provide up-to-date security configuration information for each of the FC-to-SCSI bridges. Preferably, this security information, for example, the list of device resources and authorized WWNs for every library partition, is held in non-volatile memory storage. Therefore, if a FC-to-SCSI bridge fails and is replaced, it may be reconfigured to have the same security settings as the replaced FC-to-SCSI bridge. 
     The RMC preferably allows a user to save the entire library&#39;s security configuration to a host, via a web browser, and to re-load the entire library&#39;s security configuration via the web browser. If the user wishes to set the library back to default settings or if a replacement FC tape drive that already contains security information from another library is detected, the library management firmware may reset security information by issuing a security configuration request. 
     Partition security should be persistent between power-cycles and should not require a power cycle to alter partition security. The RMC preferably detects a firmware update to any component in the library. In the event of a firmware update being detected, the RMC preferably reconfigures the security settings of the component. If the library controller detects that a FC tape drive in the library has a firmware update, or the drive is replaced and the tape drive no longer supports partitioning, then the RMC preferably configures the partitioning back to its default state. If the RMC firmware is updated then the RMC should set the security configuration of all components in the library back to the default unsecured state. 
     If the library management interface allows the user to manually change the SCSI-ID of devices that are associated to FC-to-SCSI bridges, then this operation is preferably integrated with the security system such that any SCSI-ID change via management interface also triggers a security configuration request for the affected library partition to the FC-to-SCSI bridge that is associated to the changed tape drive.