Apparatus and method to control access to logical volumes

A method to control access to logical volumes. The method provides a plurality of host computers and an information storage and retrieval system comprising a plurality of logical volumes. The method forms (N) host computer groups, assigns one or more of the host computers to the (i)th host computer group, such that each host computer assigned to (i)th host computer group is not assigned to any other of the (N) host computer groups. The method forms (N) logical volume groups, assigns one or more logical volumes to the (i)th logical volume group, such that each of the logical volumes assigned to the (i)th logical volume group is not assigned to any other of the (N) logical volume groups. The method maintains a database associating the (i)th host computer group with the (i)th logical volume group, and permits a host computer assigned to the (i)th host computer group to access a logical volume assigned to the (i)th logical volume group.

FIELD OF THE INVENTION

The invention relates to an apparatus and method to control access to logical volumes disposed in an information storage and retrieval system.

BACKGROUND OF THE INVENTION

In hierarchical computer storage systems, fast and intensively used storage are paired with arrays of slower and less frequently accessed data devices. One example of high-speed, expensive memory is a direct access storage device file buffer (DASD). Slower storage devices include tape drives and disk drive arrays. Such tape drives and/or disk drive arrays are often located in an information storage and retrieval system, sometimes referred to as an automated media storage library.

Information storage and retrieval systems are known for providing cost effective access to large quantities of stored information, such as backup computer files. Generally, such information storage and retrieval systems include information storage media, such as a plurality of tape cartridges, a plurality of optical cartridges, a plurality of disk arrays, a plurality of electronic storage media, and the like. By electronic storage media, Applicants mean a device such as a PROM, EPROM, EEPROM, Flash PROM, and the like. A number of different companies manufacture automated media storage libraries today, each model displaying various different features. One example is the IBM TotalStorage® Enterprise Storage Server.

Storage area networks (SANs) are dedicated networks that connect one or more hosts or servers to storage devices and subsystems, such as an automated media library. SANs may utilize an appliance, such as a networked attached storage device (“NASD”) to provide for management of the SAN.

What is needed is a method to control access to logical volumes disposed in an information storage and retrieval system, where multiple host computers owned by differing persons have access rights to one or more of those logical volumes.

SUMMARY OF THE INVENTION

Applicants' invention includes an apparatus and method to control access to logical volumes disposed in an information storage and retrieval system. The method provides an information storage and retrieval system comprising a plurality of logical volumes, and a plurality of host computers, where each host computer is capable of communicating with the information storage and retrieval system.

Applicants' method forms (N) host computer groups, assigns one or more of the plurality of host computers to the (i)th host computer group, where (i) is greater than or equal to 1 and less than or equal to (N), such that each host computer assigned to (i)th host computer group is not assigned to any other of the (N) host computer groups. Applicants' method forms (N) logical volume groups, assigns one or more of the plurality of logical volumes to the (i)th logical volume group, such that each of said logical volumes assigned to the (i)th logical volume group is not assigned to any other of the (N) logical volume groups.

The method maintains a database associating the (i)th host computer group with the (i)th logical volume group, and permits each of the one or more host computers assigned to the (i)th host computer group to access each logical volume comprising the (i)th logical volume group.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the illustrations, like numerals correspond to like parts depicted in the Figures.FIG. 2Ashows one embodiment of Applicants' data processing system. In the illustrated embodiment ofFIG. 2A, system200includes a first host computer210, a second host computer220, and a third host computer230. Each of the first, second, and third host computers is interconnected with a storage area network (“SAN”)240. SAN240is interconnected with information storage and retrieval system250.

FIG. 2Bshows another embodiment of Applicants' data processing system. In the illustrated embodiment ofFIG. 2B, system201includes a first host computer210, a second host computer220, a third host computer230, and information storage and retrieval system250. Each of the first, second, and third host computers is interconnected with information storage and retrieval system250.

In certain embodiments, Applicants' data processing system includes one or more host computers that communicate with information storage and retrieval system250via a SAN as illustrated inFIG. 2A, in combination with one or more host computers that communicate with information storage and retrieval system250directly as illustrated inFIG. 2B.

The illustrated embodiments ofFIGS. 2A and 2Binclude three host computers. In other embodiments, Applicants' data processing systems200/201include two host computers. In other embodiments, Applicants' data processing systems200/201include more than three host computers.

Host computer210comprises a computer system, such as a mainframe, personal computer, workstation, and combinations thereof, including an operating system212such as Windows, AIX, Unix, MVS, LINUX, etc. (Windows is a registered trademark of Microsoft Corporation; AIX is a registered trademark and MVS is a trademark of IBM Corporation; and UNIX is a registered trademark in the United States and other countries licensed exclusively through The Open Group.) In certain embodiments, host computer210further includes a second operating system218such as, for example, Windows, AIX, Unix, MVS, LINUX, etc.

In certain embodiments, host computer210includes a storage management program214. The storage management program214in the host computer210may include the functionality of storage management type programs known in the art that manage the transfer of data to a data storage and retrieval system, such as the IBM DFSMS implemented in the IBM MVS operating system.

Storage management program214may include known storage management program functions, such as recall and migration. The storage management program214may be implemented within the operating system212of the host computer210or as a separate, installed application program216. Alternatively, storage management program214may include device drivers, backup software, application programs216, and the like.

In certain embodiments, host computer220includes a storage management program224. The storage management program224in the host computer220may include the functionality of storage management type programs known in the art that manage the transfer of data to a data storage and retrieval system, such as the IBM DFSMS implemented in the IBM MVS operating system.

Storage management program224may include known storage management program functions, such as recall and migration. The storage management program224may be implemented within the operating system222of the host computer220or as a separate, installed application program226. Alternatively, storage management program214may include device drivers, backup software, application programs226, and the like.

In certain embodiments, host computer230includes a storage management program234. The storage management program234in the host computer230may include the functionality of storage management type programs known in the art that manage the transfer of data to a data storage and retrieval system, such as the IBM DFSMS implemented in the IBM MVS operating system.

Storage management program234may include known storage management program functions, such as recall and migration. The storage management program234may be implemented within the operating system232of the host computer210or as a separate, installed application program236. Alternatively, storage management program234may include device drivers, backup software, application programs236, and the like.

In the illustrated embodiment ofFIG. 2A, host computer210is capable of communicating with SAN240via a plurality of communication links219. In the illustrated embodiment ofFIG. 2A, plurality of communication links219includes communication links211,213,215, and217. In other embodiments, host computer210is capable of communicating with SAN240via fewer than four communication links. In other embodiments, host computer210is capable of communicating with SAN240via more than four communication links. In certain embodiments, communication links211,213,215, and217, are each selected from the group consisting of a serial interconnection, such as RS-232 or RS-422, an Ethernet interconnection, a SCSI interconnection, a Fibre Channel interconnection, an ESCON interconnection, a FICON interconnection, a Local Area Network (LAN), a private Wide Area Network (WAN), a public wide area network, Storage Area Network (SAN), Transmission Control Protocol/Internet Protocol (TCP/IP), the Internet, or other interconnections and/or protocols as is known to those of skill in the art.

In the illustrated embodiment ofFIG. 2A, host computer220is capable of communicating with SAN240via a plurality of communication links229. In the illustrated embodiment ofFIG. 2A, plurality of communication links229includes communication links221,223,225, and227. In other embodiments, host computer220is capable of communicating with SAN240via fewer than four communication links. In other embodiments, host computer220is capable of communicating with SAN240via more than four communication links. In certain embodiments, communication links221,223,225, and227, are each selected from the group consisting of a serial interconnection, such as RS-232 or RS-422, an Ethernet interconnection, a SCSI interconnection, a Fibre Channel interconnection, an ESCON interconnection, a FICON interconnection, a Local Area Network (LAN), a private Wide Area Network (WAN), a public wide area network, Storage Area Network (SAN), Transmission Control Protocol/Internet Protocol (TCP/IP), the Internet, or other interconnections and/or protocols as is known to those of skill in the art.

In the illustrated embodiment ofFIG. 2A, host computer230is capable of communicating with SAN240via a plurality of communication links239. In the illustrated embodiment ofFIG. 2A, plurality of communication links239includes communication links231,233,235, and237. In other embodiments, host computer230is capable of communicating with SAN240via fewer than four communication links. In other embodiments, host computer230is capable of communicating with SAN240via more than four communication links. In certain embodiments, communication links231,233,235, and237, are each selected from the group consisting of a serial interconnection, such as RS-232 or RS-422, an Ethernet interconnection, a SCSI interconnection, a Fibre Channel interconnection, an ESCON interconnection, a FICON interconnection, a Local Area Network (LAN), a private Wide Area Network (WAN), a public wide area network, Storage Area Network (SAN), Transmission Control Protocol/Internet Protocol (TCP/IP), the Internet, or other interconnections and/or protocols as is known to those of skill in the art.

SAN240comprises a storage area network, and is capable of communicating with information storage and retrieval system250via a plurality of communication links270. In the illustrated embodiment ofFIG. 2A, plurality of communication links270includes communication links272,274, and276. In other embodiments, plurality of communication links270includes fewer than three communication links. In other embodiments, plurality of communication links270includes more than three communication links. In certain embodiments, communication links272,274, and276, are each selected from the group consisting of an Ethernet interconnection, a SCSI interconnection, a Fibre Channel interconnection, an ESCON interconnection, a FICON interconnection, a Local Area Network (LAN), a private Wide Area Network (WAN), a public wide area network, Storage Area Network (SAN), Transmission Control Protocol/internet Protocol (TCP/IP), the Internet, or other interconnections and/or protocols as is known to those of skill in the art.

In the illustrated embodiment ofFIG. 2B, host computer210is capable of communicating with information storage and retrieval system250via a plurality of communication links219. In the illustrated embodiment ofFIG. 2B, plurality of communication links219includes communication links211,213,215, and217. In other embodiments, host computer210is capable of communicating with information storage and retrieval system250via fewer than four communication links. In other embodiments, host computer210is capable of communicating with information storage and retrieval system250via more than four communication links. In certain embodiments, communication links211,213,215, and217, are each selected from the group consisting of an Ethernet interconnection, a SCSI interconnection, a Fibre Channel interconnection, an ESCON interconnection, a FICON interconnection, a Local Area Network (LAN), a private Wide Area Network (WAN), a public wide area network, Storage Area Network (SAN), Transmission Control Protocol/Internet Protocol (TCP/IP), the Internet, or other interconnections and/or protocols as is known to those of skill in the art.

In the illustrated embodiment ofFIG. 2B, host computer220is capable of communicating with information storage and retrieval system250via a plurality of communication links229. In the illustrated embodiment ofFIG. 2B, plurality of communication links229includes communication links221,223,225, and227. In other embodiments, host computer210is capable of communicating with information storage and retrieval system250via fewer than four communication links. In other embodiments, host computer210is capable of communicating with information storage and retrieval system250via more than four communication links. In certain embodiments, communication links221,223,225, and227, are each selected from the group consisting of an Ethernet interconnection, a SCSI interconnection, a Fibre Channel interconnection, an ESCON interconnection, a FICON interconnection, a Local Area Network (LAN), a private Wide Area Network (WAN), a public wide area network, Storage Area Network (SAN), Transmission Control Protocol/Internet Protocol (TCP/IP), the Internet, or other interconnections and/or protocols as is known to those of skill in the art.

In the illustrated embodiment ofFIG. 2B, host computer230is capable of communicating with information storage and retrieval system250via a plurality of communication links239. In the illustrated embodiment ofFIG. 2B, plurality of communication links239includes communication links231,233,235, and237. In other embodiments, host computer210is capable of communicating with information storage and retrieval system250via fewer than four communication links. In other embodiments, host computer210is capable of communicating with information storage and retrieval system250via more than four communication links. In certain embodiments, communication links231,233,235, and237, are each selected from the group consisting of an Ethernet interconnection, a SCSI interconnection, a Fibre Channel interconnection, an ESCON interconnection, a FICON interconnection, a Local Area Network (LAN), a private Wide Area Network (WAN), a public wide area network, Storage Area Network (SAN), Transmission Control Protocol/Internet Protocol (TCP/IP), the Internet, or other interconnections and/or protocols as is known to those of skill in the art.

In the illustrated embodiments ofFIGS. 2A and 2B, information storage and retrieval system250is shown further including logical volumes251,252,253,254,255,256, and257. In other embodiments, information storage and retrieval system250comprises more than seven logical volumes. Information storage and retrieval system250further includes controller258and non-volatile memory259.

In certain embodiments, the logical volumes disposed in information storage and retrieval system250are written to one or more DASD devices. In certain embodiments, the logical volumes disposed in information storage and retrieval system are written to one or more hard disks. In certain embodiments, the logical volumes disposed in information storage and retrieval system are written to one or more hard disks, where those hard disks are configured in one or more hard disk arrays. In certain embodiments, the logical volumes disposed in information storage and retrieval system are written to one or more magnetic tapes.

In certain embodiments, Applicants' information storage and retrieval system250comprises an automated media library comprising a plurality of tape cartridges, one or more robotic accessors, and one or more tape drives. U.S. Pat. No. 5,970,030, assigned to the common assignee herein, describes such an automated media library and is hereby incorporated by reference. In certain embodiments, Applicants' information storage and retrieval system250comprises a virtual tape system. U.S. Pat. No. 6,269,423, assigned to the common assignee herein, describes such a virtual tape system, and is hereby incorporated by reference. In certain embodiments, Applicants' information storage and retrieval system250comprises information storage and retrieval system100(FIG. 1).

Referring now toFIG. 1, Applicants' information storage and retrieval system100includes a first cluster101A and a second cluster101B. Each cluster includes a processor portion130/140and an input/output portion160/170. Internal PCI buses in each cluster are connected via a Remote I/O bridge155/165between the processor portions130/140and I/O portions160/170, respectively.

Information storage and retrieval system100further includes a plurality of host adapters102-105,107-110,112-115, and117-120, disposed in four host bays101,106,111, and116. Each host adapter may comprise one or more Fibre Channel ports, FICON ports, ESCON ports, or SCSI ports. Other embodiments may have host adapters comprising ports supporting other protocols known to those skilled in the art. Each host adapter is connected to both clusters through one or more Common Platform Interconnect buses121and150such that each cluster can handle I/O from any host adapter.

I/O portion160further comprises a plurality of device adapters, such as device adapters165,166,167, and168, and sixteen disk drives organized into two disk arrays, namely array “A” and array “B”. In certain embodiments, hard disk arrays “A” and “B” utilize a RAID protocol. As those skilled in the art will appreciate, a RAID (Redundant Array of Independent Disks) rank combines multiple inexpensive disk drives into an array of disk drives to obtain performance, capacity and reliability that exceeds that of a single large drive.

In certain embodiments, arrays “A” and “B” comprise what is sometimes called a JBOD array, i.e. “Just a Bunch Of Disks” where the array is not configured according to RAID. The illustrated embodiment ofFIG. 1shows two hard disk arrays. In other embodiments, Applicants' information storage and retrieval system includes more than two hard disk arrays.

Hard disk array “A” includes disk drives181,182,183,184,191,192, and193. Hard disk array “B” includes disk drives185,186,187,188,195,196,197, and198. In the illustrated embodiment ofFIG. 1, each loop includes at least two spare disks, namely disks184and195. Each of the hard disk arrays includes one of those spare disks.

Referring again toFIGS. 2A and 2B, in certain embodiments, host computer210is owned by a first person. In certain embodiments, host computer220is owned by a second person. In certain embodiments, host computer230is owned by a third person. In certain embodiments, two or more of the first person, the second person, and/or the third person, differ. As those skilled in the art will appreciate, it is desirable to limit access by, for example, the first person to only logical volumes comprising information owned by that first person. Similarly, it is desirable to limit access by the second person and by the third person to logical volumes comprising information owned by that second person or third person, respectively.

In certain embodiments, the storage system which includes information storage and retrieval system250, and optionally one or more storage area networks, such as storage area network240, is owned by a fourth person. In certain embodiments, that fourth person differs from the first person, the second person, and/or the third person. In order to limit the access by the first person, and/or the second person, and/or the third person, to some but not all the logical volumes disposed in information storage and retrieval system250, the fourth person must implement an apparatus and method to control access to the logical volumes disposed in information storage and retrieval system250.

Applicants' invention includes a method to control access to logical volumes disposed in an information storage and retrieval system.FIG. 3summarizes certain initial steps in Applicants' method.

Referring now toFIG. 3, in step310Applicants' method provides an information storage and retrieval system, such as system250(FIG. 2), where that information storage and retrieval system includes a plurality of logical volumes, such as plurality of logical volumes262,264,266,268,272,274,276.

In step320, Applicant's method provides a plurality of host computers, such as host computer210,220,230, where each of those host computers are capable of communicating with the information storage and retrieval system.

In step330, Applicant's method forms (N) host computer groups, where (N) is equal to or greater than 1. In certain embodiments, one or more of those host computer groups includes one host computer. In certain embodiments, one or more of those host computer groups includes two or more host computers. In certain embodiments, step330is performed by a storage system owner and/or operator, such as the owner and/or operator of information storage and retrieval system250(FIG. 2). In certain embodiments, step330is performed by a controller, such as controller258, disposed in Applicants' information storage and retrieval system.

In certain embodiments, Applicants' method includes step340wherein the method creates and assigns a unique and persistent identifier to each of the plurality of interconnected host computers. In certain embodiments, the unique identifier assigned to a host computer in step340comprises a World Wide Node Name. In certain embodiments, the unique identifier assigned to a host computer in step340comprises one or more World Wide Port Name.

In certain embodiments, Applicants' method assigns to each host computer one or more World Wide Port Names (“WWPNs”), where each I/O port disposed in that host computer could be assigned a different WWPN. Thus, a host computer comprising (M) ports could be assigned (M) different WWPNs. Using these prior art methods, host computer210could comprise four different WWPNs, i.e. a different WWPN for each of adapters211,213,215, and217.

In certain embodiments, step340is performed by a storage system owner and/or operator, such as the owner and/or operator of information storage and retrieval system250(FIG. 2). In certain embodiments, step340is performed by a controller, such as controller258, disposed in Applicants' information storage and retrieval system.

In step350, Applicants' method assigns each host computer capable of communicating with the information storage and retrieval system to one of the (N) host computer groups. In certain embodiments, step350is performed by a storage system owner and/or operator, such as the owner and/or operator of information storage and retrieval system250(FIG. 2). In certain embodiments, step350is performed by a controller, such as controller258, disposed in Applicants' information storage and retrieval system.

In step360, Applicants' method forms (N) logical volume groups. In certain embodiments, step360is performed by a storage system owner and/or operator, such as the owner and/or operator of information storage and retrieval system250(FIG. 2). In certain embodiments, step330is performed by a controller, such as controller258, disposed in Applicants' information storage and retrieval system.

In step370, Applicants' method assigns one or more of the plurality of logical volumes of step310to one or more of the (N) logical volume groups of step360, such that each assigned logical volume is assigned to a single logical volume group. In certain embodiments, step370is performed by a storage system owner and/or operator, such as the owner and/or operator of information storage and retrieval system250(FIG. 2). In certain embodiments, step370is performed by a controller, such as controller258, disposed in Applicants' information storage and retrieval system. In the event one or more logical volumes are not assigned to any of the (N) logical volumes groups, then those volumes remain “unassigned.”

In step380, Applicants' method maintains a database, where that database associates each of the (N) host computer groups with the corresponding logical volume group. In certain embodiments, the database of step380also associates each unique identifier assigned in step340to one of the (N) host computer groups. In certain embodiments, the database of step380is saved in non-volatile memory, such as memory259, disposed in Applicants' information storage and retrieval system.

Applicants' method transitions from step380to step410(FIG. 4).FIG. 4summarizes additional steps in Applicants' method to control access to the plurality of logical volumes disposed on Applicants' information storage and retrieval system250(FIG. 2). Referring now toFIG. 4, in step410Applicants' information storage and retrieval system, such as system200(FIG.2A)/201(FIG. 2B), receives a request from an interconnected host computer, such as host computer210(FIG. 2), to access a designated logical volume, such as logical volume262(FIG. 2).

In certain embodiments, the request of step410includes addressing information that Applicants' information storage and retrieval system uses to determine the unique identifier assigned to the requesting host in step340(FIG. 3). In embodiments wherein the requesting host communicates with Applicants' information storage and retrieval system via a Fibre Channel link, the relationship between the unique identifier assigned in step340and the Fibre Channel link address is established through a Fibre Channel login process.

In step420, Applicants' method determines that the requesting host is assigned to the (j)th host computer group, wherein (j) is greater than or equal to 1 and less than or equal to (N). In certain embodiments, step420is performed by a controller, such as controller258(FIG. 2), disposed in Applicants' information storage and retrieval system, such as system250(FIG. 2).

Applicants' method transitions from step420to step430wherein the method determines if the designated logical volume of step410is assigned to the (j)th logical volume group. In certain embodiments, step420is performed by a controller, such as controller258(FIG. 2), disposed in Applicants' information storage and retrieval system, such as system250(FIG. 2).

If Applicants' method determines in step430that the designated logical volume of step410is assigned to the (j)th logical volume group, then the method transitions to step450wherein the method permits the requesting host computer, assigned to the (j)th host computer group, to access the designated logical volume which is assigned to the (jth logical volume group. Alternatively, if Applicants' method determines in step430that the designated logical volume of step410is not assigned to the (j)th logical volume group, then the method transitions to step440wherein the method does not permit the requesting host computer, assigned to the (j)th host computer group, to access the designated logical volume which is not assigned to the (j)th logical volume group.

FIG. 5summarizes additional steps in Applicants' method, wherein access rights to one or more logical volumes is changed. Referring now toFIG. 5, in certain embodiments step510includes receiving a request made by the owner/operator of a host computer group by the owner of the storage system.

The request of step510may include assigning and/or unassigning one or more host computers from a host computer group, and/or assigning and/or unassigning one or more logical volumes from a logical volume group. The steps of Applicants' method summarized inFIG. 5are used to change the access rights to logical volumes disposed in an information storage and retrieval system, where those logical volumes are not in a copy services relationship, and where parallel access volumes are not used.

Controlling access rights to logical volumes where one or more of those logical volumes may be in a copy services relationship is described in an application entitled “Apparatus and Method to Control Access to Logical Volumes Using Copy Services”, filed on even date herewith and assigned to common assignee hereof. Controlling access rights to logical volumes where one or more of those logical volumes comprises a base logical volume for one or more parallel access volumes is described in an application entitled “Apparatus and Method to Control Access to Logical Volumes Using Parallel Access Volumes”, filed on even date herewith and assigned to common assignee hereof.

In response to a request to change access rights, Applicants' method transitions to step520wherein the method determines if the request includes unassigning one or more host computers from a host computer group, such as for example the (k)th host computer group, where that request is made by the owner/operator of the (k) host computer group. If Applicants' method determines in step520that the owner/operator of the (k)th host computer group does not request that one or more host computers currently assigned to the (k)th host compute group be unassigned, then the method transitions from step520to step530. If Applicants' method determines in step520that the owner/operator of the (k)th host computer group requests that one or more host computers currently assigned to the (k)th host computer group be unassigned, then the method transitions from step520to step525wherein the method unassigns those one or more host computers. In certain embodiments, step525is performed by the, owner/operator of the storage system.

Applicants' method transitions from step525to step530, wherein the method determines if the owner/operator of the (k)th host computer group requests that one or more additional host computers be assigned to the host computer group. If Applicants' method determines in step530that the owner/operator of the (k)th host computer group does not request that one or more additional host computers be assigned to the host computer group, then Applicants' method transitions from step530to step540. Alternatively, if Applicants' method determines in step530that the owner/operator of the (k)th host computer group requests that one or more additional host computers be assigned to the host computer group, then Applicants' method transitions to step535wherein the method assigns those one or more additional host computers to the (k)th host computer group. In certain embodiments, step535is performed by the owner/operator of the storage system.

Applicants' method transitions from step535to step540, wherein the method determines if the owner/operator of the (k)th host computer group requests that one or more logical volumes assigned to the (k)th logical volume group be unassigned. If Applicants' method determines in step540that the owner/operator of the (k)th host computer group does not request one or more logical volumes assigned to the (k)th logical volume group be unassigned, then Applicants' method transitions from step540to step550. Alternatively, if Applicants' method determines in step540that the owner/operator of the (k)th host computer group requests that one or more logical volumes assigned to the (k)th logical volume group be unassigned, then Applicants' method transitions to step545wherein the method unassigns those one or more logical volumes from the (k)th logical volume group. In certain embodiments, step535is performed by the owner/operator of the storage system.

Applicants' method transitions from step545to step550, wherein the method determines if the owner/operator of the (k)th host computer group requests that one or more logical volumes be assigned to the (k)th logical volume group. If Applicants' method determines in step550that the owner/operator of the (k)th host computer group does not request that one or more logical volumes be assigned to the (k)th logical volume group, then Applicants' method transitions from step550to step560and ends.

Alternatively, if Applicants' method determines in step550that the owner/operator of the (k)th host computer group requests that one or more logical volumes be assigned to the (k)th logical volume group, then Applicants' method transitions to step552wherein the method assigns one or more logical volumes to the (k)th logical volume group. In certain embodiments, step552is performed by the owner/operator of the storage subsystem. Applicants' method transitions from step552to step554wherein the storage system owner/operator assigns identifiers to the logical volumes assigned in step552, and provides those identifiers to the owner/operator of the (k)th host computer system. In certain embodiments, Applicants' method transitions from step554to step560and ends.

In certain embodiments, a host computer assigned to the (k)th host computer group can utilize an auto configuration process or discovery techniques to locate the logical volumes newly-added to the (k)th logical volume group. In other embodiments, Applicants' method includes step556wherein the owner/operator of the (k)th host computer group revises the (k)th host computer Input/Output Control Dataset (“IOCDS”) to define access rights to the newly-assigned logical volumes of step552. Applicants' method transitions from step556to step560and ends.

The embodiments of Applicants' method recited inFIGS. 3,4, and/or5, may be implemented separately. Moreover, in certain embodiments, individual steps recited inFIGS. 3,4, and/or5, may be combined, eliminated, or reordered.

In certain embodiments, Applicants' invention includes instructions residing in non-volatile memory259(FIG. 2), where those instructions are executed by controller258(FIG. 2) to performs steps330,340,350,360,370, and380inFIG. 3, and/or steps410through450recited inFIG. 4, and/or steps520through560recited inFIG. 5. In other embodiments, Applicants' invention includes instructions residing in any other computer program product, where those instructions are executed by a computer external to, or internal to, system200(FIG.2A)/201(FIG. 2B), to perform steps330,340,350,360,370, and380inFIG. 3, and/or steps410through450recited inFIG. 4. In either case, the instructions may be encoded in an information storage medium comprising, for example, a magnetic information storage medium, an optical information storage medium, an electronic information storage medium, and the like. By “electronic storage media,” Applicants mean, for example, a device such as a PROM, EPROM, EEPROM, Flash PROM, compactflash, smartmedia, and the like.