Abstract:
An administrator&#39;s work load increases because the administrator has to both allocate volumes of PC server device applications and take over volumes for applications based on changes in PC server devices. A volume management system solves the problem with a computer system having storage devices each having a unit managing volume configuration information based on each application, a unit managing volume usage information based on the application volumes, and a unit managing and partitioning allocatable areas of the storage devices based on performance and reliability. The system has a unit selecting suitable allocation regions in accordance with the volume usages of the applications; a unit selecting a suitable allocation region based on change of host performance and migrating a volume to the suitable allocation region when the host configuration of an application changes; and a unit changing configuration information to perform change of setting on each host.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application is a Continuation application of U.S. application Ser. No. 12/314,276 filed Dec. 8, 2008. Priority is claimed from U.S. application Ser. No. 12/314,276 filed on Dec. 8, 2008, which claims priority from Japanese Patent Application No. 2008-266967, filed on Oct. 16, 2008, the entire disclosure of which is incorporated herein by reference. 
     
    
     1. FIELD OF THE INVENTION 
       [0002]    The present invention relates to a volume management system in a computer system in which disks equivalent to local disks of host computers are integrated into network-type storage devices so that the host computers can use these disks via a storage area network (SAN). 
       2. DESCRIPTION OF THE RELATED ART 
       [0003]    Network-type storage devices (hereinafter referred to as storage devices) which can be connected to host computers by iSCSI (internet Small Computer System Interface) or FC (Fibre Channel) have come into practical use in recent years. In a computer system using such storage devices, the storage devices are logically partitioned into storage areas called LUs (Logical Units) so that each host can use the LUs in place of local HDDs (Hard Disk Drives). 
         [0004]    Although mainframe/server devices were usually chiefly used as the host computers, inexpensive PC (Personal Computer) server devices have been used widely as the host computers with the advance of popularization and cost reduction of the storage devices. In a system using such PC server devices, the number of the PC server devices is large and each PC server device is frequently replaced with a new one because of device failure, upgrade of device performance, etc. compared with a system using the mainframe/server devices. For this reason, the work load imposed on an administrator increases because the administrator has heretofore performed the work of allocating volumes to applications of the PC server devices (such as generation of LUs, setting of paths to the generated LUs, and setting of paths to the PC server devices) and the work of taking over volumes for applications in accordance with replacement of PC server devices (such as changing of the paths to the generated LUs, and changing of the paths to the PC server devices). JP-A-2006-92054 has been proposed on a configuration change process at the time of volume migration. 
       SUMMARY OF THE INVENTION 
       [0005]    The related art system is designed so that when a volume is migrated between storage devices, each computer can be connected to the migration destination volume without interruption. In the related art system, it is possible to lighten the load imposed on the administrator at the time of volume migration but it is impossible to lighten the load imposed on the administrator with respect to volume generation, environment setting work concerned with migration between computers, etc. 
         [0006]    An object of the invention is to provide a function of lightening the load imposed on an administrator for a volume generation and configuration change process by managing volumes used by applications in accordance with the applications and using characteristics of the applications and information about host environments where the applications are operated. 
         [0007]    The volume management system in the computer system according to the invention is a volume management system in a computer system having storage devices each of which has a unit which manages volume configuration information in accordance with each application, a unit which manages volume usage information in accordance with each of volumes for the applications, and a unit which manages allocatable areas of the storage devices while partitioning the allocatable areas of the storage devices in accordance with performance and reliability, wherein the volume management system has: a unit which selects suitable allocation regions in accordance with the volume usages of the applications; a unit which selects a suitable allocation region in accordance with change of host performance and migrates a volume to the suitable allocation region when host configuration of an application is changed; and a unit which changes configuration information to perform change of setting on each host. 
         [0008]    According to the invention, generation of volumes and setting change work due to change in host configuration can be performed by each storage device in accordance with the volume usages of the applications, so that the number of administrator&#39;s operations can be reduced. In addition, allocation of volumes can be decided in accordance with the volume usages of the applications, so that a problem concerned with performance competition among the applications can be prevented in advance. Further, when a problem such as HDD failure occurred in a storage device, the storage device can identify a host and an application related to the problem. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is an explanatory diagram showing the schematic configuration of a computer system according to Embodiment 1 of the invention; 
           [0010]      FIG. 2  is an explanatory diagram conceptually showing the internal configuration of each host in Embodiment 1 of the invention; 
           [0011]      FIG. 3  is an explanatory diagram conceptually showing the configuration of hosts and volumes for configuration change in Embodiment 1 of the invention; 
           [0012]      FIG. 4  is an explanatory diagram conceptually showing the configuration of hosts and volumes after the configuration change in Embodiment 1 of the invention; 
           [0013]      FIG. 5  is an explanatory diagram conceptually showing the internal configuration of each storage device in Embodiment 1 of the invention; 
           [0014]      FIG. 6  is an explanatory view of an AP management table stored in a memory of each storage device in Embodiment 1 of the invention; 
           [0015]      FIG. 7  is an explanatory view of the AP management table stored in a memory of each storage device after the configuration change in Embodiment 1 of the invention; 
           [0016]      FIG. 8  is an explanatory view of a resource management table stored in a memory of each storage device in Embodiment 1 of the invention; 
           [0017]      FIG. 9  is an explanatory view of an AP registration table stored in a memory of each host in Embodiment 1 of the invention; 
           [0018]      FIG. 10  is a flow chart showing a configuration change process in Embodiment 1 of the invention; 
           [0019]      FIG. 11  is an explanatory diagram conceptually showing the configuration of a host and volumes in an allocation process in Embodiment 2 of the invention; 
           [0020]      FIG. 12  is an explanatory view of an AP registration table concerned with the allocation process in Embodiment 2 of the invention; 
           [0021]      FIG. 13  is an explanatory view of a resource management table concerned with the allocation process in Embodiment 2 of the invention; 
           [0022]      FIG. 14  is an explanatory view of an AP management table stored in a memory of each storage device after configuration change in Embodiment 2 of the invention; 
           [0023]      FIG. 15  is a flow chart showing the allocation process in Embodiment 2 of the invention; 
           [0024]      FIG. 16  is a sequence diagram showing the configuration change process in Embodiment 1 of the invention; and 
           [0025]      FIG. 17  is a sequence diagram showing the allocation process in Embodiment 2 of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Embodiments of the invention will be described below with reference to the drawings. 
       Embodiment 1 
       [0027]    First, the configuration of a system according to the invention will be described. The schematic configuration of a computer system according to an embodiment of the invention will be described with reference to  FIGS. 1 ,  2  and  5 .  FIG. 1  is an explanatory diagram showing the schematic configuration of the computer system according to the embodiment.  FIG. 2  is an explanatory diagram conceptually showing the internal configuration of each host in the embodiment.  FIG. 5  is an explanatory diagram conceptually showing the internal configuration of a controller of each storage device in the embodiment. 
         [0028]    As shown in  FIG. 1 , the computer system according to the embodiment includes hosts  100 , and storage devices  300 . The hosts  100  are used by users. The storage devices  300  have logical units (LUs)  600  used by the hosts. The hosts  100  and the storage devices  300  are connected to one another through an IP (Internet Protocol) network  800 . The IP network  800  is a local area network (LAN) which is constructed by Ethernet (registered trademark) and which uses TCP/UDP/IP (Transmission Control Protocol/User Datagram Protocol/Internet Protocol) as a communication protocol for execution of data transmission. In this embodiment, an iSCSI protocol is used for communication between the hosts  100  and the storage devices  300 . Alternatively, an FC protocol may be used for communication between the hosts  100  and the storage devices  300 . In this case, an FC network is used between the hosts  100  and the storage devices  300 . 
         [0029]    Each Storage device  300  has a controller  400 , and a plurality of magnetic hard disk drives (HDDs)  500 . The storage device  300  is a disk array device in which each redundant array of independent disks (RAID) is made up of a plurality of HDDs  500 . The storage device  300  provides one or a plurality of RAID groups (RAID-G)  700  each having an RAID structure. Each RAID-G  700  provides one or a plurality of logical volumes. Each logical volume is also called logical unit (LU)  600 . 
         [0030]    As shown in  FIG. 5 , the controller  400  of each storage device  300  has a CPU (Central Processing Unit)  401 , a memory  402 , a disk I/O (Input/Output) interface  403 , a host I/O interface  404 , and a management I/O interface  405  inside thereof. The CPU  401 , the memory  402  and the I/O interfaces  403 ,  404  and  405  are connected to one another through a bus. The CPU  401  is a processing unit which executes various programs stored in the memory  402 . The memory  402  is a so-called internal storage device including both a nonvolatile memory for storing various programs etc. and a volatile memory for temporarily storing results of processing. The disk I/O interface  403  is connected to the HDDs  500 . The host I/O interface  404  is connected to the hosts  100  through the IP network  800 . The management I/O interface  405  is connected to a management computer (not shown) through the IP network  800 . 
         [0031]    The memory  402  stores an AP (Application) management table  410 , a resource management table  411 , a disk access program  412  and an allocation management program  413 . 
         [0032]    The AP management table  410  is an area where information about applications and information about storage resources allocated to the applications are stored. The resource management table  411  is an area where information on capacities and use statuses of RAID-Gs are stored. The disk access program  412  receives read/write commands for LUs from the host I/O interface  404  and executes these commands by using the disk I/O interface  403 . The allocation management program  413  is a program related to the system according to the invention and provided for performing a volume allocating process. 
         [0033]    As shown in  FIG. 2 , each host  100  has a CPU  101 , a memory  102 , and an I/O interface  103  inside thereof. The CPU  101 , the memory  102  and the I/O interface  103  are connected to one another through a bus. The CPU  101  is a processing unit which executes various programs stored in the memory  102 . The memory  102  is a so-called internal storage device including both a nonvolatile memory for storing various programs etc. and a volatile memory for temporarily storing results of processing. The I/O interface  103  is connected to the storage devices  300  through the IP network  800 . 
         [0034]    The memory  102  stores an AP registration table  110 , an iSCSI processing program  111  and an allocating program  112 . The iSCSI processing program  111  is a program which transmits SCSI I/O commands issued from the OS (Operating System) of each host to the storage devices  300  by use of the TCP/IP protocol. The allocating program  112  is a program related to the system according to the invention. The allocating program  112  generates volumes of applications called from a discovery process of the iSCSI processing program  111  and registered in the AP registration table  110  and performs volume configuration change. 
         [0035]    The LU configuration of the storage devices according to the embodiment will be described below with reference to  FIG. 3 . The iSCSI processing program  111  of each host  100  is connected to the storage devices  300  by using ID information called target. As for iSCSI, the target information contains an IP address for identifying a port of the host I/O interface  404 , a target name, and an initiator name. One or more logical units are mapped for one target. When a host  100  is connected to a target of a storage device  300 , one or more LUs mapped for the target are mounted on the host  100 . In this system, applications AP-A and AP-B are operated in each host and each of the applications has at least one target and at least one LU. 
         [0036]    The configuration of the AP registration table in  FIG. 2  will be described below with reference to  FIG. 9 . The AP registration table  110  is a table in which volumes of applications to be subjected to volume allocation and configuration change are registered. The AP registration table  110  is information which is set in each host by an administrator. In the AP registration table, identifiers for identifying applications uniquely in the system are registered in a column “APID”  1101 . In addition, identifiers for individually identifying a plurality of volumes of an application are registered in a column “Volume ID”  1102 . Port addresses of storage devices where volumes are generated are set in a column “Port Address”  1103  by the allocating program  112 . 
         [0037]    Successively, the configuration of the AP management table in  FIG. 5  will be described with reference to  FIG. 6 . The AP management table  410  contains an AP table  410 - 1 , a volume table  410 - 2 , an AP-volume correspondence table  410 - 3  and a volume-RAID-G correspondence table  410 - 4 . 
         [0038]    When volumes are allocated to applications, the AP table  410 - 1  is generated by the allocation management program  413  of the controller  400  of each storage device  300 . The AP table  410 - 1  has a column “Host ID Information”  41012  for identifying each host where an application is located, a column “OS Type”  41013  for identifying an OS operated in the host, a column “Host Performance”  41014  for expressing CPU performance of the host, a column “AP Type”  41015  for expressing the type of the application, and a column “APID”  41011  for identifying the application. IP addresses of hosts can be used in the column “Host ID Information”  41012 . OS names can be used in the column “OS Type”  41013 . Clock values of CPUs can be used in the column “Host Performance”  41014 . Application names can be used in the column “AP Type”  41015 . 
         [0039]    The volume table  410 - 2  is a table in which characteristics of volumes used by applications are described. When volumes are allocated to applications, the volume table  410 - 2  is generated by the allocation management program  413  of the controller  400  of each storage device  300 . The volume table  410 - 2  has a column “APID”  41021  for identifying each application, a column “Volume ID”  41022  for identifying each individual volume used by the application, a column “Format Characteristic”  41023  for expressing a volume formatting method performed by the application, and a column “Data Type”  41024  for expressing data stored in the volume by the application. Since there are two cases, i.e. the case where the application performs formatting on all of the volume and the case where the application performs formatting on part of the volume, the column “Format Characteristic”  41023  is used for discriminating between these two cases. There are a DB type, a text type, an image type, etc. as the type of data stored in the volume. The column “Data Type”  41024  is used for identifying the type of data. 
         [0040]    The AP-volume correspondence table  410 - 3  is a table in which information about paths of volumes allocated to applications is described. When volumes are allocated to applications, the AP-volume correspondence table  410 - 3  is generated by the allocation management program  413  of the controller  400  of each storage device  300 . The AP-volume correspondence table  410 - 3  has a column “Target Name”  41033 , a column “Port Address”  41034 , and a column “Initiator Name”  41035 . 
         [0041]    The volume-RAID-G correspondence table  410 - 4  is a table in which information about RAID groups having the volumes generated therein is described. When volumes are allocated to applications, the volume-RAID-G correspondence table  410 - 4  is generated by the allocation management program  413  of the controller  400  of each storage device  300 . A column “RAID-G”  41043  indicates generated RAID-Gs. A column “LU Number”  41044  indicates generated LUs. A column “IO Performance”  41045  indicates average IO performance values of volumes. After allocation, the column “IP Performance”  41045  is periodically set by the allocation management program  413 . 
         [0042]    The configuration of the resource management table in  FIG. 5  will be described below with reference to  FIG. 8 . The resource management table  411  contains a device information table  411 - 1 , and an RAID-G information tale  411 - 2 . The device information table  411 - 1  is a table in which information about storage devices  300  allowed to be subjected to volume allocation is described. The device information table  411 - 1  is information which is set in each storage device by the administrator in advance. The device information table  411 - 1  has a column “Device ID”  41111  for identifying a device, and a column “Management Port Address”  41112  which is used when the allocation management program  413  communicates with the allocation management program  413  of another controller. 
         [0043]    The RAID-G information table  411 - 2  is a table in which information about RAID-Gs generated in the respective storage devices is described. Information of the respective storage devices is set by the administrator in advance. The allocation management program  413  of the controller  400  of each storage device  300  can acquire the RAID-G information table  411 - 2  from devices registered in the device information table  411 - 1 . A column “RAID-G”  41122  indicates information for identifying an RAID-G in the device. A column “HDD Type”  41123  indicates the type of HDDs (SAS, SATA, or the like) forming the RAID group. The RAID-G can be changed in accordance with usages such as reliability and performance. 
         [0044]    A column “Region Allocation Method”  41124  indicates whether the RAID-G has a function of allocating a region to an LU statically or dynamically. As for the static allocation function, HDDs are allocated to the LU in advance. As for the dynamic allocation function, HDDs are allocated to the LU only when WRITE occurs in the LU, so that the used capacity of the HDDs can be reduced. A column “Number of IOs”  41126  indicates the total number of IOs for each volume in the RAID group. After allocation, the column “Number of IOs”  41126  is periodically set by the allocation management program  413  of the controller  400  of each storage device  300 . 
         [0045]    The outline of a configuration change process will be described below with reference to  FIGS. 3 to 9 .  FIG. 10  is a flow chart showing the configuration change process.  FIG. 16  is a sequence diagram showing the configuration change process. 
         [0046]    The configuration change mentioned herein is based on the assumption that after volumes are allocated to AP-A and AP-B in a host  100 - 1 , AP-B is migrated to a host  100 - 2  so that the load imposed on the host  100 - 1  can be shared. The configuration change process is a process by which the volume allocated to AP-B is permitted to be used in the host  100 - 2 . An allocation process for newly allocating a volume to an application will be described in Embodiment 2. 
         [0047]      FIG. 3  is a diagram showing the LU configuration before the configuration change.  FIG. 4  is a diagram showing the LU configuration after the configuration change. The reference numeral  110 - 1  designates the AP registration table of the host  100 - 1  before the configuration change. The reference numeral  110 - 2  designates the AP registration table of the host  100 - 2  before the configuration change. The reference numeral  110 - 1 A designates the AP registration table of the host  100 - 1  after the configuration change. The reference numeral  110 - 2 A designates the AP registration table of the host  100 - 2  after the configuration change. The reference numerals  410 - 1 A,  410 - 3 A and  410 - 4 A designate the AP table, the AP-volume correspondence table and the volume-RAID-G correspondence table, respectively, after the configuration change. 
         [0048]    As shown in  FIG. 9 , the administrator deletes information about an APID (AP-B) from the AP registration table  110 - 1  of the host  100 - 1  and registers the APID (AP-B) and a volume ID (VOL 1 ) in the AP registration table  110 - 2  of the host  100 - 2 . 
         [0049]    The administrator operates the iSCSI processing program  111  of the host  100 - 2  to execute discovery. The allocating program  112  of the host  100 - 2  receives a discovery request. The allocating program  112  performs a volume configuration change process for the APID (AP-B) because a port address for the APID (AP-B) has not been registered in the AP registration table  110 - 2  yet. 
         [0050]    Although the allocating program  112  displays a parameter input screen in the flow chart of the configuration change process in  FIG. 10 , the administrator does not input any value because the process is for configuration change. In the volume allocating process of the host  100 - 2 , an iSCSI initiator name, host ID information and performance information of the host  100 - 2  are acquired from OS configuration information and an allocation request is sent to the allocation management program  413  of each storage device  300 . 
         [0051]    In step S 1001  of  FIG. 10 , the allocation management program  413  confirms registration of the APID (AP-B) on each storage device. In step S 1002 , the configuration change process is performed because the APID (AP-B) has been already registered in the AP table  410 - 1  in  FIG. 6 . For the configuration change process, the allocation management program  413  acquires the value of host performance  41014  from the AP table  410 - 1  based on the acknowledged APID. When a new value of host performance is higher than the registered value of host performance, the allocation management program  413  performs a volume migration process by selecting an RAID-G capable of providing higher IO performance than the current IO performance in the following procedure. Assume now that the CPU performance of the host  100 - 1  is 1.0 GHz and the CPU performance of the host  100 - 2  is 2.0 GHz which is higher than that of the host  100 - 1 . When the RAID-G cannot be selected, the migration process is not performed but the routine of processing goes to step S 1009  in which a path change process of the storage device will be performed. 
         [0052]    The volume migration process is performed as follows. First, in step S 1003 , the allocation management program  413  updates the RAID-G information table by collecting RAID-G information tables from allocation management programs  413  of other devices. In step S 1004 , the allocation management program  413  selects RAID-Gs consistent with a region allocation method  41124  of the currently allocated RAID-G. In step  1005 , the allocation management program  413  selects RAID-Gs capable of providing higher IO performance than the current IO performance from the selected RAID-Gs in accordance with the HDD type  41123 . In step S 1006 , the allocation management program  413  selects RAID-Gs lower in IO load and smaller in the number of IOs from the selected RAID-Gs in accordance with the number of IOs  41126 . In step  1007 , the allocation management program  413  selects an RAID-G capable of storing all the volume of AP-B from the selected RAID-Gs in accordance with the free capacity  41125 . If there are RAID-Gs obtained, an arbitrary RAID-G is selected from the obtained RADI-Gs. 
         [0053]    In step S 1008 , the allocation management program  413  copies the volume into the selected RAID-G by using the copy function of the storage device. RAID-G information after migration is reflected on the volume-RAID-G correspondence table  410 - 4 A ( FIG. 7 ) in the AP management table  410 . In this example, the allocation management program  413  selects device ID ( 0 ) and RAID-G ( 1 ) from the RIAD-G information table  411 - 2  ( FIG. 8 ) in the resource management table  411  and copies an LU in the device. When the selected RAID-G is in another device, the allocation management program  413  allocates a new target, maps the LU on the target and changes the respective AP management tables  410  of the migration source and destination storage devices. 
         [0054]    In the step S 1009 , the allocation management program  413  registers the acknowledged iSCSI initiator name in the target by the path change process. The allocation management program  413  registers the iSCSI initiator name in the AP-volume correspondence table  410 - 3 A ( FIG. 7 ) and sets the host ID information in the AP table  410 - 1 A. In step S 1010 , the allocation management program  413  notifies the allocating program  112  of the completion of the configuration change. The allocation management program  413  notifies the allocating program  112  of the port address of the target at which the volume has been generated. In step S 1011 , the allocating program  112  sets the acknowledged port address of the target in the AP registration table  110 - 2 A ( FIG. 9 ). The allocating program  112  registers the port address in the iSCSI processing program  111 . Thus, processing is terminated. 
         [0055]    After the aforementioned processing, the iSCSI processing program  111  continues the discovery process which is performed on the port address of the set target. By the discovery process, the disk access program  412  notifies the iSCSI processing program  111  of the name of the target in which the iSCSI initiator name has been registered. The iSCSI processing program  111  performs a log-in process on the acknowledged target to access the migration destination volume. 
       Embodiment 2 
       [0056]    A process for allocating a new volume to an application will be described with reference to  FIGS. 11 ,  12 ,  13 ,  15  and  17 . 
         [0057]      FIG. 11  is a diagram showing the LU configuration after new registration of an application. The reference numeral  110 - 2  designates the AP registration table of the host  100 - 2 . As shown in  FIG. 12 , the reference numeral  110 - 2 A designates the AP registration table before AP registration, and the reference numeral  110 - 2 B designates the AP registration table after AP registration. As shown in  FIG. 14 , the reference numerals  410 - 1 B,  410 - 2 B,  410 - 3 B and  410 - 4 B designate the AP table, the volume table, the AP-volume correspondence table and the volume-RAID-G correspondence table, respectively, after AP registration. 
         [0058]      FIG. 15  is a flow chart showing an allocation process in Embodiment 2 of the invention.  FIG. 17  is a sequence diagram showing the allocation process in Embodiment 2 of the invention. 
         [0059]    An administrator registers an APID (AP-C) and a volume ID (VOL 1 ) in the AP registration table  110 - 2 A ( FIG. 12 ). 
         [0060]    The administrator operates an iSCSI processing program to execute discovery. An allocating program  112  receives a discovery request. The allocating program  112  performs a volume allocation process for the APID (AP-C) because the port address for the APID (AP-C) has not been registered in the AP registration table  110 - 2 A yet. 
         [0061]    In step S 2001  in  FIG. 15 , the allocating program  112  displays a parameter input screen and the administrator enters the APID (AP-C), the AP type of VOL  1 , format characteristic, the data type and the size on the parameter input screen. For the volume allocation process, the allocating program  112  acquires the iSCSI initiator name, host ID information and host performance information of the host  100 - 2  from OS configuration information and sends an allocation request to an allocation management program  413  of a storage device  300 . 
         [0062]    The allocation management program  413  performs the allocation process as follows. First, in step S 2002 , the allocation management program  413  updates an RAID-G information table by collecting RAID-G information tables from allocation management programs  413  of other devices. The reference numeral  411 - 2 B designates the updated RAID-G information table ( FIG. 13 ). In step S 2003 , the allocation management program  413  obtains a region allocation method in accordance with the value of format characteristic and selects RAID-Gs consistent with the region allocation method. For example, a virtual region can be selected for a volume partially formatted because virtual allocation can be used for the volume. In step S 2004 , the allocation management program  413  selects RAID-Gs capable of providing higher IO performance from the RAID-Gs selected in accordance with the performance requirement, in accordance with the HDD type  41123 . When, for example, the volume has the AP type “DB” and the data type “DB”, HDD high in reliability and performance is selected. When, for example, the volume has the data type “File”, HDD different from the HDD for “DB” is selected because the performance requirement for “File” can be made lower than that for “DB”. 
         [0063]    In step S 2005 , the allocation management program  413  selects RAID-Gs lower in IO load and smaller in the number of IOs from the selected RAID-Gs in accordance with the number of IOs  41126 . In step  2006 , the allocation management program  413  selects an RAID-G capable of storing the volume of AP-C from the selected RAID-Gs in accordance with the free capacity  41125 . In step S 2007 , the allocation management program  413  generates an LU in the selected RAID-G. The allocation management program  413  allocates a target and reflects information after LU generation on the AP management table  410 . When the selected RAID-G is in another device, the allocation management program  413  notifies the allocation management program  413  of the other device of the selected RAID group so that the allocation management program  413  of the other device performs generation of an LU, generation of a target and updating of the AP management table  410 . 
         [0064]    In step S 2008 , the allocation management program  413  registers an iSCSI initiator name in the target by a path setting process. The allocation management program  413  sets the iSCSI initiator name and host ID information in the AP management table  410 . The reference numerals  410 - 1 B,  410 - 2 B,  410 - 3 B and  410 - 4 B designate the updated tables ( FIG. 14 ). In step S 2009 , the allocation management program  413  notifies the allocating program  112  of the completion of the allocation. The allocation management program  413  notifies the allocating program  112  of the port address of the target at which the volume has been generated. In step S 2010 , the allocating program  112  sets the acknowledged port address of the target in the AP registration table  110 - 23  ( FIG. 12 ). The allocating program  112  registers the port address in the iSCSI processing program  111 . Thus, processing is terminated. 
         [0065]    After the aforementioned processing, the iSCSI processing program  111  continues the discovery process which is performed on the port address of the set target. By the discovery process, the disk access program  412  notifies the iSCSI processing program  111  of the name of the target for which the iSCSI initiator name has been registered. The iSCSI processing program  111  performs a log-in process on the acknowledged target to access the generated volume.