Abstract:
Disclosed is to prevent deterioration in I/O performance of a computer resulted from a use of the same physical disk among different logical volumes.  
     A volume management server  1010  groups together logical volumes which use the same physical disk of a storage device  1020  as a volume group and allocates a storage area on the physical disk to be used on a priority basis by this volume group to the volume group, and thereby a physical arrangement according to a present physical arrangement of the logical volume can be performed when an automatic expansion of the logical volume is performed thereafter so that the I/O performance deterioration of the computer caused by a mutual interference is avoided at the time of access from the computer  1030  to the storage device  1020.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     The present invention contains subject matter related to Japanese Patent Application JP 2005-311676 filed in the Japanese Patent Office on Oct. 26, 2005, the entire contents of which being incorporated herein by reference.  
       BACKGROUND  
       [0002]     The present invention relates to a storage system used for a computer system, and more particularly the present invention relates to a method of expanding a volume capacity at the time of writing into a storage system from a computer system.  
         [0003]     Generally, a computer system is comprised of a computer that performs each individual job and a storage device that reads and writes data in accordance with a command of the computer. The storage device has a plurality of physical disks to store and read out data, and manages the physical disks by dividing into a plurality of storage areas.  
         [0004]     Accordingly, the storage device can provide the storage area to the computer in a form of a logical volume. This logical volume is comprised of a plurality of segments and is a unit of a logical storage capacity that makes it possible to read and write data in accordance with the command of the computer by allocating the storage area on the physical disk to each segment. The capacity of this logical volume can be expanded at any time according to a necessity.  
         [0005]     For example, when the computer uses up the logical volume provided by the storage device, the computer can expand the logical volume capacity by creating a logical volume from an unused storage area of a physical disk in the storage device and by combining this logical volume with the logical volume in use. Such a method is called on-line volume expansion.  
         [0006]     However, in this on-line volume expansion, an administrator of the storage device needs to perform a series of operations until the volume expansion is completed. Therefore, when a sudden increase of the capacity occurs in computer systems of a plurality of enterprises in such a large scale data center that the plurality of enterprises use simultaneously, there occurs a possibility that requests for on-line volume expansion are generated simultaneously such that the administrator of the storage device is not able to cope with. In the worst case, there has been such a problem that it was not possible to perform the on-line volume expansion and processing of the computer stopped.  
         [0007]     Then, in order to solve a request of a user and administrator of a storage system, the patent reference  1 , for example, discloses such a method that a storage device creates a storage area from an unused area in a physical disk while a computer is on-line and adds dynamically to a segment of a logical volume during on-line access when a capacity of the logical volume in the storage device becomes insufficient due to writing from the computer. Such method is called a volume capacity automatic expansion.  
         [0008]     This volume capacity automatic expansion is to make an allocation of an unallocated area of a physical disk to a logical volume when there is a request for writing from a computer. The on-line volume expansion can be automatically performed without an intervention of an administrator of a storage device by this volume capacity automatic expansion.  
         [0009]     [Patent Reference 1] Japanese Patent Application Publication No. 2003-15915  
       SUMMARY  
       [0010]     However, in the above-described prior art, it is practiced that the storage device creates the storage area from the unused area in the physical disk while the computer is on-line and adds dynamically to the storage area of the logical volume during the on-line access when the capacity of the logical volume in the storage device becomes insufficient due to the writing into the logical volume from the computer.  
         [0011]     At this time, the allocation is made sequentially from an empty area without taking it into consideration that a storage area created from an unused area of which physical disk should be added to the storage area of the logical volume. Accordingly, physical disks used by the same logical volume are dispersed and there is such an inconvenience that deterioration in I/O performance of the computer occurs due to a mutual interference resulted from a use of the same physical disk among different logical volumes.  
         [0012]     Then, the present invention aims at preventing deterioration in I/O performance of a computer by preventing generation of a mutual interference among different logical volumes when the volume capacity automatic expansion of a logical volume is performed.  
         [0013]     In order to solve the above-described problem and achieve the aim of the present invention, a computer system of the present invention is a computer system that includes a plurality of host computers, a plurality of storage systems, and a management computer, wherein the above-described management computer has a processor, and this processor executes an information collection program to acquire volume allocation information and physical disk information which are retained in the above-described storage system; and a storage area allocation program to set priority allocation storage area information in which an allocation area is limited depending on an existence or nonexistence of an already allocated area based on the above-described volume allocation information and above-described physical disk information when an storage area of a physical disk is allocated to a logical volume of the above-described storage system.  
         [0014]     In addition, a storage area allocation method of the present invention is a storage area allocation method in a computer system which includes a plurality of host computers, a plurality of storage systems, and a management computer, wherein the above-described management computer is used in order to acquire volume allocation information and physical disk information which are retained in the above-described storage system by using an information collection program and to set priority allocation storage area information in which an allocation area is limited depending on an existence or nonexistence of an already allocated area based on the above-described volume allocation information and above-described physical disk information by using a storage area allocation program when a storage area of a physical disk is allocated to a logical volume of the above-described storage system.  
         [0015]     Also, a management computer of the present invention is a management computer to control a plurality of storage systems that store data used by a plurality of host computers on a plurality of volumes, wherein a memory; a hard disk; a processor to perform control; an input device to give the above-described storage system a command to set a priority allocation storage area; an output device to notify a completion of setting the priority allocation storage area from the above-described storage system; and a communication port to perform communication of management data with the above-described storage system are equipped, a management table that is generated based on volume allocation information and physical disk information which are retained in the above-described storage system; an information collection program to collect information from the above-described storage system; a storage area allocation program to allocate a storage area of a physical disk to a logical volume of the above-described storage system; and an information transmission program to transmit storage area allocation information of the above-described allocation to the above-described storage system are stored and provided in the above-described hard disk, and the control is performed such that the above-described information collection program acquires the volume allocation information and physical disk information which are retained in the above-described storage system and that the above-described storage area allocation program sets priority allocation storage area information in which an allocation area is limited depending on an existence or nonexistence of an already allocated area based on the above-described volume allocation information and above-described physical disk information when a storage area of a physical disk is allocated to a logical volume of the above-described storage system.  
         [0016]     According to the present invention, the automatic expansion of the logical volume can be performed in consideration of the physical disk that includes the storage area to be allocated by setting the priority allocation storage area information in which the allocation area is limited depending on the existence or nonexistence of the already allocated area and by determining beforehand the storage area on the physical disk which is allocated on a priority basis to the logical volume even when the volume capacity automatic expansion of the logical volume is performed, and it is possible to prevent the generation of the mutual interference among the different logical volumes and to prevent the deterioration of the I/O performance of the computer.  
         [0017]     In addition, logical volumes which use the same physical disk are grouped together as a volume group, a storage area on a physical disk which is used on a priority basis by this volume group is allocated to the volume group, and thereby a physical arrangement according to a present physical arrangement of the logical volume can be performed in such a manner that an already allocated volume group remains as is allocated; another volume group is allocated separately; and a volume group which can share the same physical disk is allocated on a priority basis, for example, when an automatic expansion of a logical volume is performed thereafter. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a diagram showing an example of an outline configuration of a storage management system;  
         [0019]      FIG. 2  is a diagram showing a configuration of a volume management server;  
         [0020]      FIG. 3  is a diagram showing a configuration of a storage device;  
         [0021]      FIG. 4  is a flow chart showing processing in the volume management server;  
         [0022]      FIG. 5  is a flow chart showing processing in an information collection program of the volume management server;  
         [0023]      FIG. 6  is a flow chart showing processing to input an item of an already allocated physical disk of a volume management table by the information collection program of the volume management server;  
         [0024]      FIG. 7  is a flow chart showing processing of a storage area allocation program of the volume management server;  
         [0025]      FIG. 8  is a flow chart showing processing to create a volume group by the storage area allocation program of the volume management server;  
         [0026]      FIG. 9  is a flow chart showing processing to allocate a priority physical disk to a volume group by the storage area allocation program of the volume management server;  
         [0027]      FIG. 10  is a flow chart showing processing to allocate a priority allocation storage area to a logical volume by the storage area allocation program of the volume management server;  
         [0028]      FIG. 11  is a diagram showing a volume allocation management table that is retained in the storage device;  
         [0029]      FIG. 12  is a diagram showing a physical disk allocation management table that is retained in the storage device;  
         [0030]      FIG. 13  is a diagram showing a priority allocation management table that is retained in the storage device;  
         [0031]      FIG. 14  is a diagram showing a volume management table that is retained in the volume management server;  
         [0032]      FIG. 15  is a diagram showing a physical disk management table that is retained in the volume management server;  
         [0033]      FIG. 16  is a diagram showing a volume group management table that is retained in the volume group management server;  
         [0034]      FIG. 17  is a diagram showing priority allocation storage area information that is transmitted from the volume allocation server to the storage device; and  
         [0035]      FIG. 18  is a flow chart showing another processing in the volume management server. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]     Hereinafter, embodiments of the present invention are explained more specifically by referring to the accompanied drawings when appropriate.  
         [0037]      FIG. 1  is an outline diagram of a storage management system which is applied to an embodiment of the present invention. As shown in this figure, the storage management system of the present embodiment is comprised of a volume management server  1010 , a plurality of computers  1030 , and a plurality of storage devices  1020 .  
         [0038]     An administrator  1060  gives the volume management server  1010  a command to set a priority allocation storage area by taking an opportunity of an optimization completion of a logical volume in the storage device  1020 , an addition of a physical disk, and the like.  
         [0039]     Although the volume management server  1010  is connected with the storage device  1020  through a management network  1040  and the computer  1030  is connected with the storage device  1020  through a storage area network  1050  in the present embodiment, the management network  1040  and storage area network  1050  may be the same network.  
         [0040]      FIG. 2  is a diagram showing a configuration of the volume management server  1010 .  
         [0041]     The volume management server  1010  is comprised of a CPU  2010 , a memory  2020 , a hard disk  2030 , an input device  2040  for the administrator  1060  to input a command to set a priority allocation storage area, an output device  2050  to notify the administrator  1060  that the setting of the priority allocation storage area is completed, and a communication port  2060  which is an interface to communicate management data with the storage device  1020 .  
         [0042]     Three programs which are an information collection program  2110  to collect volume allocation information and physical disk information form the storage device  1020 , a storage area allocation program  2120  to generate priority allocation storage area information  17000  from the collected volume allocation information and physical disk information, and an information transmission program  2130  to transmit the priority allocation storage area information  17000  to the storage device  1020  are provided in the hard disk  2030 .  
         [0043]     In addition, a volume management table  2210  to manage a volume on the storage device  1020 , a physical disk management table  2220  to manage a physical disk  3030  on the storage device  1020 , and a volume group management table  2230  to manage information of a grouped volume on the storage device  1020  are included in the hard disk  2030 .  
         [0044]     When the command to set the priority allocation storage area is received from the administrator  1060 , the volume management server  1010  having such configuration transmits the priority allocation storage area information  17000  to the storage device  1020  after acquiring the volume allocation information and physical disk information from the storage device  1020  and producing the priority allocation storage area information  17000  shown in  FIG. 17  which is described later.  
         [0045]      FIG. 3  is a diagram showing a configuration of the storage device  1020 . The storage device  1020  is comprised of an I/O port  3040  which is an interface used for communication with the computer  1030 , a management port  3050  which is an interface used for communication of management data, a plurality of physical disks  3030 , a controller  3010  which controls the storage device  1020 , and a memory  3020 . The plurality of physical disks  3030  are allocated to different logical volumes  3210 ,  3220 ,  3230 , and  3240 .  
         [0046]     A volume allocation management table  3110  to manage volume allocation information of the storage device  1020 , which is shown in later-described  FIG. 11 , a physical disk allocation management table  3120  to manage the physical disk  3030  of the storage device  1020 , which is shown in later-described  FIG. 12 , a priority allocation management table  3130  to manage a physical volume to allocate on a priority basis to a logical volume, which is shown in later-described  FIG. 13 , are included in the memory  3020 .  
         [0047]     The volume allocation management table  3110  shown in  FIG. 11  is comprised of a volume ID  11010  to identify a logical volume, a segment ID  11020  to identify a segment in the logical volume, an LBA start  11030  to show an LBA start address of the segment in the logical volume, an LBA end address  11040  to show an LBA end address of the segment in the logical volume, and an allocated storage area ID  11050  to identify a storage area allocated to the segment in the volume.  
         [0048]     The physical disk allocation management table  3120  shown in  FIG. 12  is comprised of a physical disk ID  12010  to identify a physical disk  3030 , a storage area ID  12020  to identify a storage area included in the physical disk  3030 , and a remaining capacity  12030  in the physical disk  3030 .  
         [0049]     The priority allocation management table  3130  shown in  FIG. 13  is comprised of a volume ID  13010  and a priority allocation storage area ID  13020  to identify a storage area allocated on a priority basis to the volume.  
         [0050]     When a request for writing into a logical volume is received through the I/O port  3040 , the storage device  1020  confirms whether a storage area is allocated to an address of the corresponding logical volume.  
         [0051]     When a storage area is not allocated to this address of the logical volume, contents of the request for writing is written after an unused storage area among storage areas allocated on a priority basis to the corresponding logical volume in the priority allocation management table  3130  shown in  FIG. 13  is allocated to the logical volume. When a storage area is allocated to this address of the logical volume, the contents of the request for writing is written.  
         [0052]     When the storage device  1020  receives a request for volume allocation information through the management port  3050 , information included in the volume allocation management table  3110  that is retained in the memory  3020  is transmitted to a transmission source of the request for the volume allocation information as the volume allocation information.  
         [0053]     In addition, when the storage device  1020  receives a request for physical disk information through the management port  3050 , information included in the physical disk allocation management table  3120  that is retained in the memory  3020  is transmitted to a transmission source of the request for the physical disk information as the physical disk information.  
         [0054]     Moreover, when the storage device  1020  receives the priority allocation storage area information  17000  through the management port  3050 , the priority allocation management table  3130  retained in the memory  3020  is renewed with the contents of the received priority allocation storage area information  17000 .  
         [0055]     Although an example in which the volume management server  1010  and the storage device  1020  operate in different devices is shown in the present embodiment, the present invention is not limited to this embodiment and it is possible to configure such that each program to execute processing performed in the volume management server  1010  is retained in the memory  3020  of the storage device  1020 .  
         [0056]     Hereinafter, an explanation is made to an operation of the volume management server  1010  in the present embodiment.  
         [0057]      FIG. 4  is a flow chart showing an outline of processing in the volume management server  1010 .  
         [0058]     First, the volume management server  1010  collects volume allocation information and physical disk information from the storage device  1020  by using the information collection program  2110  (step S 4010 ).  
         [0059]     More precisely, the CPU  2010  of the volume management server  1010  collects each information of the volume allocation management table  3110  shown in  FIG. 11  and physical disk allocation management table  3120  shown in  FIG. 12  by reading out the information collection program  2110  and executing processing of an information collection module.  
         [0060]     Next, information collection processing (step S 4010 ) in the information collection program  2110  is explained.  
         [0061]     First, an explanation is made to each table which is generated by this information collection program  2110 .  
         [0062]     The volume management table  2210  shown in  FIG. 14  is comprised of a volume ID  14010 , an allocated storage area ID  14020 , an allocated physical disk ID  14030  to identify a physical disk which is allocated to a logical volume, a volume group ID  14040  to identify a volume group to which the logical volume belongs, a priority allocation physical disk ID  14050  to identify a physical disk which includes a storage area to allocate on a priority basis to the logical volume, a priority allocation storage area ID  14060  to identify the storage area to allocate on the priority basis to the logical volume.  
         [0063]     The physical disk management table  2220  shown in  FIG. 15  is comprised of a physical disk ID  15010 , a storage area ID  15020 , a remaining capacity  15030 , and an allocation volume group ID  15040  to identify a volume group to allocate a physical disk.  
         [0064]      FIG. 5  is a flow chart showing an outline of processing in the information collection program  2110 .  
         [0065]     First, the information collection program  2110  transmits a request for volume allocation information to the storage device  1020  (step S 5010 ).  
         [0066]     Next, the information collection program  2110  receives volume allocation information that is a response from the storage device  1020 , and saves this information in the volume management table  2210  shown in  FIG. 14  (step S 5020 ).  
         [0067]     Here, the information collection program  2110  adds a volume ID to the volume ID of the volume management table  2210  when this volume ID of the volume allocation information does not exist in the volume ID of the volume management table  2210 , and executes nothing when this volume ID exists therein.  
         [0068]     In addition, the information collection program  2110  adds an allocated storage area ID of the volume allocation information to a record having identical volume ID in the volume management table  2210  by setting a delimitation using a comma.  
         [0069]     Furthermore, as to the other information included in the volume allocation information, the information collection program  2110  does not save that information in the volume management table  2210 .  
         [0070]     Next, the information collection program  2110  transmits a request for physical disk information to the storage device  1020  (step S 5030 ).  
         [0071]     Subsequently, the information collection program  2110  receives physical disk information that is a response from the storage device  1020 , and saves this information in the physical disk management table  2220  shown in  FIG. 15  (step S 5040 ).  
         [0072]     Here, the information collection program  2110  saves a physical disk ID of the physical disk information in the physical disk ID of the physical disk management table  2220 .  
         [0073]     In addition, the information collection program  2110  saves a storage area ID of the physical disk information in a storage area ID of a record having the identical physical disk ID in the physical disk management table  2220 .  
         [0074]     Furthermore, the information collection program  2110  saves a remaining capacity of the physical disk information in the remaining capacity of the record having the identical physical disk ID in the physical disk management table  2220 .  
         [0075]     Next, the information collection program  2110  inputs an item of the allocated physical disk of the volume management table  2210  (step S 5050 ).  
         [0076]      FIG. 6  is a flow chart showing an outline of processing (step S 5050 ) in which the information collection program  2110  inputs the item of the allocated physical disk of the volume management table  2210  shown in  FIG. 14 .  
         [0077]     First, the information collection program  2110  confirms whether there is a logical volume to which the allocated physical disk ID is not input yet in the volume management table  2210  shown in  FIG. 14  (step S 6010 ).  
         [0078]     When it is judged that there is no record in the volume management table  2210  to which the allocated physical disk ID is not input yet (step S 6020 ), the information collection program  2110  ends the processing to input the item of the allocated physical disk of the volume management table  2210 .  
         [0079]     When it is judged that there is a record in the volume management table  2110  to which the allocated physical disk ID is not input yet (step S 6030 ), a physical disk ID of a storage area that has the identical allocated storage area ID is acquired from the physical disk management table  2220  (step S 6110 ).  
         [0080]     Next, it is confirmed whether the acquired physical disk ID is already written in the allocated physical disk ID of a corresponding record of the volume management table  2110  (step S 6210 ).  
         [0081]     When it is judged that this physical disk ID is already registered (step S 6220 ), the process returns to the processing (step S 6010 ) to confirm whether there is a record to which the allocated physical disk ID is not input yet.  
         [0082]     When it is judged that this physical disk ID is not registered (step S 6230 ), the acquired physical disk ID is added to the allocated physical disk ID of this record of the volume management table  2210  (step S 6310 ), and the process returns to the processing (step S 6010 ) to confirm whether there is a record to which the allocated physical disk ID is not input yet.  
         [0083]     The above is an explanation of the processing in which the information collection program  2110  inputs the item of the allocated physical disk of the volume management table  2210  shown in  FIG. 14 .  
         [0084]     Returning to  FIG. 4 , the volume management server  1010  allocates a priority allocation storage area by using the storage area allocation program  2120  (step S 4020 ).  
         [0085]     More precisely, the CPU  2010  of the volume management server  1010  executes the allocation processing by reading out the storage area allocation program  2120  and executing processing of the storage area allocation module.  
         [0086]      FIG. 7  is a flow chart showing an outline of the allocation processing (step S 4020 ) of the priority allocation storage area of the storage area allocation program  2120 .  
         [0087]     First, the storage area allocation program  2120  creates a volume group (step S 7010 ).  
         [0088]      FIG. 8  is a flow chart showing an outline of the processing (step S 7010 ) to create the volume group in the storage area allocation program  2120 .  
         [0089]     First, a table generated by the storage area allocation program  2120  is explained.  
         [0090]     The volume group management table  2230  shown in  FIG. 16  is comprised of a volume group ID  16010  to identify a volume group, a volume ID  16020  to identify a volume which is included in the volume group, and a physical disk ID  16030  to identify a physical disk which is allocated to the volume group.  
         [0091]     Returning to an explanation of  FIG. 8 , first the storage area allocation program  2120  confirms whether there is an unprocessed record in the volume management table  2210  (step S 8010 ).  
         [0092]     When it is judged that there is no unprocessed record (step S 8020 ), the storage area allocation program  2120  searches for a record which includes the volume ID of the volume management table  2210  from the volume group management table  2230  shown in  FIG. 16 , inputs a volume group ID of this record into the volume group ID of the volume management table  2210  (step S 8110 ), and ends the processing to create the volume group.  
         [0093]     When it is judged that there is an unprocessed record (step S 8030 ), it is confirmed whether a record that includes the allocated physical disk ID of this record of the volume management table  2210  in an item of the physical disk ID exists in the volume group management table  2230  (step S 8210 ).  
         [0094]     When it is judged that the record that includes the allocated physical disk ID of this record of the volume management table  2210  in the item of the physical disk ID does not exist in the volume management table  2230  (step S 8220 ), a volume group ID that does not exist in the volume group management table  2230  is created.  
         [0095]     Then, a new record whose volume group ID is the newly created volume group ID described in the above and whose physical disk ID is the allocated physical disk ID of this record of the volume management table  2210  is added to the volume group management table  2230  (step S 8310 ), and the process returns to the processing (step S 8010 ) to confirm whether there is an unprocessed record in the volume management table  2210 .  
         [0096]     At this time, as a method of creating the volume group ID, there is a method of making one by adding 1 to the maximum integer number among integer numbers in use in case that a new addition is made by allocating an integer number to the volume group ID, for example.  
         [0097]     When it is judged that a record that includes the allocated physical disk ID of this record of the volume management table  2210  in the item of the physical disk ID exists in the volume group management table  230  (step S 8230 ), it is confirmed whether the physical disk ID that is included in the item of the allocated physical disk ID of this record of the volume management table  2210  is distributed over a plurality of records in the physical disk ID of the volume group management table  2230  (step S 8410 ).  
         [0098]     When it is judged that there is only one volume group in which the same physical disk ID is included (step S 8420 ), the volume ID of this record of the volume management table  2210  is added to the volume ID of the record of the corresponding volume group ID among the records included in the volume management table  2230  (step S 8510 ), and the process returns to the processing (step S 8010 ) to confirm whether there is an unprocessed record in the volume management table  2210 .  
         [0099]     When it is judged that there are a plurality of volume groups in which the same physical disk ID is included (step S 8430 ), a volume group ID that does not exist in the volume group management table  2230  is created. Further, a new record whose volume group ID is the newly created volume group ID described in the above and which includes all the physical disk IDs included in the record of the volume group in which the above-described same physical disk is included is added to the volume group management table  2230  (step S 8610 ).  
         [0100]     Furthermore, the record of the volume group in which the above-described same physical disk is included is deleted from the volume group management table  2230 . Thereafter, the process returns to the processing (step S 8010 ) to confirm whether there is an unprocessed record in the volume management table  2210 .  
         [0101]     The above is an explanation of the processing to create the volume group in the storage area allocation program  2120 .  
         [0102]     Returning to  FIG. 7 , the storage area allocation program  2120  allocates a priority physical disk to a volume group (step S 7020 ).  
         [0103]      FIG. 9  is a flow chart showing an outline of the processing (step S 7020 ) to allocate the priority physical disk to the volume group in the storage area allocation program  2120 .  
         [0104]     The storage area allocation program  2120  first confirms whether the processing is performed to all the records that are included in the physical disk management table  2220  (step S 9010 ).  
         [0105]     When the processing is completed to all the records that are included in the physical disk management table  2220  (step S 9020 ), the storage area allocation program  2120  ends the processing to allocate the priority physical disk to the volume group.  
         [0106]     When it is judged that there is an unprocessed record among the records included in the physical disk management table  2220  (step S 9030 ), the storage area allocation program  2120  executes following processing to the record included in the physical disk management table  2220 .  
         [0107]     First, the storage area allocation program  2120  confirms whether the physical disk of this record of the physical disk management table  2220  is allocated to a volume group by using the allocation volume group ID of this record of the physical disk management table  2220  (step S 9110 ).  
         [0108]     When it is judged that the physical disk of this record of the physical disk management table  2220  is already allocated to the volume group (step S 9120 ), no change is performed (step S 9210 ) since this physical disk is used continuously by this volume group, and the process returns to the processing (step S 9010 ) to confirm whether the processing is performed to all the records included in the physical disk management table  2220 .  
         [0109]     When it is judged that the physical disk of this record of the physical disk management table  2220  is not allocated to a volume group (step S 9130 ), this physical disk is allocated to a volume group having the least remaining capacity (step S 9310 ), and the process returns to the processing (step S 9010 ) to confirm whether the processing is performed to all the records included in the physical disk management table  2220 .  
         [0110]     At this time, the following can be considered as a method of searching for the volume group having the least remaining capacity.  
         [0111]     The storage area allocation program  2120  can calculate the remaining capacity of the volume group included in the volume group management table  2230  to each record of the volume group management table  2230  by acquiring the remaining capacity of the record having the identical physical disk ID from the physical disk management table  2220 .  
         [0112]     A volume group whose remaining capacity is the least in the above calculation is the volume group having the least remaining capacity among the records having the identical physical disk ID.  
         [0113]     The above is an explanation of the processing in which the priority physical disk is allocated to the volume group in the storage area allocation program  2120 .  
         [0114]     Returning to  FIG. 7 , the storage area allocation program  2120  allocates the priority allocation storage area to the logical volume at the end (step S 7030 ).  
         [0115]      FIG. 10  is a flow chart showing an outline of the processing (step S 7030 ) to allocate the priority allocation storage area to the logical volume in the storage area allocation program  2120 .  
         [0116]     The storage area allocation program  2120  first confirms whether the processing is performed to all the records included in the volume management table  2210  (step S 10010 ). When the processing is completed to all the records included in the volume management table  2210  (step S 10020 ), the storage area allocation program  2120  ends the processing to allocate the priority allocation storage area to the logical volume.  
         [0117]     When it is judged that there is an unprocessed record among the records included in the volume management table  2210  (step S 10030 ), a record whose volume group ID is identical with the volume group ID of this record is searched from the volume group management table  2230 , and it is confirmed whether a plurality of volume IDs are included in a value of the volume ID of the above-described record having the identical volume group ID (step S 10110 ).  
         [0118]     When it is judged that the plurality of volume IDs are included in the value of the volume group ID of the above-described record having the identical volume group ID (step S 10120 ), an unallocated storage area among storage areas that are included in a physical disk allocated to this volume group is allocated evenly to a logical volume comprising this volume group as a priority allocation storage area, and a storage area ID of the above-described allocated storage area is added to the priority allocation storage area ID of this record of the volume management table  2210  (step S 10410 ).  
         [0119]     Then, the process returns to the processing (step S 10010 ) to confirm whether the processing is performed to all the records included in the volume management table  2210 .  
         [0120]     When it is judged that only one volume ID is included in the volume group ID of the above-described record having the identical volume group ID (step S 10130 ), an unallocated storage area among storage areas that are included in a physical disk allocated to this volume group is allocated as a priority allocation storage area of the above-described one volume ID, and a storage area ID of the above-described allocated storage area is added to the priority allocation storage area ID of this record of the volume management table  2210  (step S 10510 ).  
         [0121]     Then, the process returns to the processing (step S 10010 ) to confirm whether the processing is performed to all the records included in the volume management table  2210 .  
         [0122]     The above is an explanation of the processing to allocate the priority allocation storage area to the logical volume in the storage area allocation program  2120 .  
         [0123]     Next, a table generated by the storage area allocation program  2120  is explained.  
         [0124]     Priority allocation storage area information  17000  shown in  FIG. 17  is comprised of a volume ID  17010  and a priority allocation storage area ID  17020 .  
         [0125]     Returning to  FIG. 4 , the volume management server  1010  transmits the priority allocation storage area information  17000  shown in  FIG. 17  at the end to the storage device  1020  by using the information transmission program  2130  (step S 4030 ).  
         [0126]     More precisely, the information transmission program  2130  of the volume management server  1010  makes the CPU  2010  materialize an information transmission module so that transmission processing is executed by the information transmission program  2130 .  
         [0127]     The information transmission program  2130  creates the priority allocation storage area information  17000  from the volume ID and priority allocation storage area ID that are included in the volume management table  2210 , and transmits this information to the storage device  1020 .  
         [0128]     Next, the volume management server  1010  uses the output device  2050  to notify the administrator  1060  that the setting of the priority allocation storage area is completed.  
         [0129]     The above is an explanation of the operation of the volume management server  1010  in the present invention.  
         [0130]     According to the present embodiment, an automatic allocation of a storage area on a physical disk to a logical volume, which is equivalent to prior-art mapping of a physical disk to a logical volume, becomes possible even in the storage device  1020  that performs the automatic expansion of a logical volume, and it is possible to expand automatically a logical volume while maintaining the I/O performance of the logical volume.  
         [0131]     Hereinafter, another embodiment is explained by using the accompanied drawings.  
         [0132]     In another embodiment, a point where an add-on notice reception program is retained in a hard disk  2030  of a volume management server  18010  in the configuration of the previous embodiment shown in  FIG. 2  is a different point from the aforementioned embodiment.  
         [0133]     In addition, when a physical disk is added, the storage device  1020  transmits an add-on notice to notify the addition of the physical disk to the volume management server  18010  that is set beforehand.  
         [0134]     Hereinafter, an operation of the volume management server  18010  in another embodiment is explained.  
         [0135]      FIG. 18  is a flow chart showing an outline of processing of the volume management server  18010  in another embodiment.  
         [0136]     First, the volume management server  18010  waits that an add-on notice is notified from the storage device  1020  by an add-on notice reception program  19110 .  
         [0137]     When the transmitted add-on notice is received by the storage device  1020 , the add-on notice reception program  19110  commands the information collection program  2110  to collect volume allocation information and physical volume information (step S 20010 ).  
         [0138]     Nest, the volume management server  18010  collects the volume allocation information and physical disk information from the storage device  1020  by the information collection program  2110  (step S 4010 ). Processing performed in the information collection program  2110  is similar to the previous embodiment.  
         [0139]     Next, the volume management server  18010  allocates a priority allocation storage area by the storage area allocation program  2120  (step S 4020 ) . Processing performed in the storage area allocation program  2120  is similar to the previous embodiment.  
         [0140]     Next, the volume management server  18010  transmits the priority allocation storage area information  17000  shown in  FIG. 17  to the storage device  1020  by the information transmission program  2130  (step S 4030 ). Processing performed in the information transmission program  2130  is similar to the previous embodiment.  
         [0141]     It should be noted that the add-on notice transmitted from the storage device  1020  to the volume management server  16010  is executed by using a trap module, for example. The trap module carries out a notification of start, stop, and state change such as port information, for example.  
         [0142]     In addition, the add-on notice may be notified regularly or at arbitrary timing during an I/O decrease by an administrator.  
         [0143]     Here, when the I/O decrease occurs, the above-described priority allocation is performed after executing a volume migration once and optimizing a system so that the volume migration becomes unnecessary thereafter.  
         [0144]     The above is an explanation of the operation of the volume management server  18010  in another embodiment.  
         [0145]     According to the present embodiment, an allocation of a storage area on a physical disk to a logical volume, which is equivalent to the prior-art mapping of a physical disk to a logical volume, becomes possible without an intervention of an administrator even in the storage device  1020  that performs the automatic expansion of a logical volume, and it is possible to expand automatically a logical volume while maintaining the I/O performance of the logical volume.  
         [0146]     Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments and that various changes and modifications could be effected therein by one skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.