Abstract:
In accordance with an aspect of the invention, a storage system includes a processor; a memory; a disk control module configured to receive a write command for writing to an unallocated area and to identify an object of the write command to be written as a written object; and an object allocation acquisition module configured to obtain object allocation information specifying one or more virtual volume locations for storing the written object. The disk control module allocates, to each of the one or more virtual volume locations, an area selected from a plurality of logical volumes if the written object is predefined as a randomly accessed object. The disk control module allocates to the one or more virtual volume locations a consecutive area of one logical volume if the written object is predefined as a sequentially accessed object.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to storage systems with thin provisioning and, more particularly, to the allocation of an area of logical volume to a virtual volume. 
     In recent years, thin provisioning has become popular. Thin provisioning is a method for allocating an area to a virtual volume when a storage subsystem receives a write command to an unallocated area. Existing methods allow a thin provisioning function to allocate an area randomly selected from several logical volumes to a virtual volume. Therefore, sequential access will become random access. When the storage subsystem receives sequential read command to consecutive areas, the response time will increase because the storage subsystem accesses randomly distributed areas and each HDD seeks a target sector. Sequential access performance will decrease. On the other hand, if the thin provisioning function allocates an area sequentially selected from one logical volume to a virtual volume, a lot of random accesses go to only the logical volume. Random access performance will decrease. An example for managing virtual volumes in a utility storage server system is found in U.S. Pat. No. 6,823,442. 
     BRIEF SUMMARY OF THE INVENTION 
     Exemplary embodiments of the invention provide a disk control program that allocates an area having portions selected from several logical volumes or a consecutive area of one logical volume based on predefined information when the disk control program receives a write command to an unallocated area. According to a first embodiment, an object allocation acquisition program obtains object allocation information. The disk control program identifies a written object when the disk control program receives a write command to an unallocated area. The disk control program allocates an area having portions selected from several logical volumes when the written object is predefined as a randomly accessed object. The disk control program allocates a consecutive area of one logical volume when the written object is predefined as a sequentially accessed object. According to a second embodiment, the disk control program identifies a target volume when the disk control program receives a write command to an unallocated area. The disk control program allocates an area having portions selected from several logical volumes when the target volume is predefined as a randomly accessed volume. The disk control program allocates a consecutive area of one logical volume when the target volume is predefined as a sequentially accessed volume. 
     In accordance with an aspect of the present invention, a storage system comprises a processor; a memory; a disk control module configured to receive a write command for writing to an unallocated area and to identify an object of the write command to be written as a written object; and an object allocation acquisition module configured to obtain object allocation information specifying one or more virtual volume locations for storing the written object. The disk control module allocates, to each of the one or more virtual volume locations, an area selected from a plurality of logical volumes if the written object is predefined as a randomly accessed object. The disk control module allocates to the one or more virtual volume locations a consecutive area of one logical volume if the written object is predefined as a sequentially accessed object. 
     In some embodiments, the disk control program is configured to update virtual volume information correlating one or more logical volume locations of the allocated area with the one or more virtual volume locations for storing the written object. The one or more logical volume locations include a logical volume name and one or more logical volume addresses, and wherein the one or more virtual volume locations include a virtual volume name and one or more virtual volume addresses. The disk control program is configured to obtain the one or more virtual volume locations for storing the written object from the object allocation information; obtain one or more logical volume locations corresponding to the obtained one or more virtual volume locations based on virtual volume information; obtain one or more RAID group names and addresses corresponding to the obtained one or more logical volume locations based on logical volume information; obtain a media name corresponding to the obtained one or more RAID group names and addresses based on RAID group information; and write data of the write command to media corresponding to the obtained media name. 
     In specific embodiments, the disk control program is configured to obtain the one or more virtual volume locations for storing the written object from the object allocation information, obtain one or more logical volume locations corresponding to the one or more virtual volume locations based on virtual volume information, and obtain one or more RAID group names and addresses corresponding to the obtained one or more logical volume locations based on logical volume information. If the written object is predefined as a randomly accessed object, then for the area to be allocated to each one of the one or more virtual volume locations, the disk control module selects from the one or more RAID group names and addresses a RAID group which has a least amount of assigned capacity, selects a logical volume which is associated with the selected RAID group, and allocates a portion of the selected logical volume as the selected area to the one virtual volume location. If the written object is predefined as a sequentially accessed object and if the disk control module finds a virtual volume name and virtual volume address of an adjacent previous address of an object address of the written object, the disk control program obtains the virtual volume name and virtual volume address of the adjacent previous address from the object allocation information, obtains a logical volume name and a logical volume address allocated to the virtual volume name and the virtual volume address of the adjacent previous address, obtains an adjacent subsequent address of the logical volume address of the adjacent previous address, and allocates an area of the adjacent subsequent address as the consecutive area of one logical volume to the one or more virtual volume locations for storing the written object. If the written object is predefined as a sequentially accessed object and if the disk control module does not find a virtual volume name and virtual volume address of an adjacent previous address of an object address of the written object, the disk control program allocates an area of a logical volume of a RAID group for which an access type is SEQUENTIAL. 
     In some embodiments, the storage system further comprises a move module. An access type of the written object is changed to a changed object from a randomly accessed object to a sequentially accessed object or from a sequentially accessed object to a randomly accessed object. If the access type of the changed object is changed from a sequentially accessed object to a randomly accessed object, the changed object has an object name and a plurality of object addresses, and for each object address of the object addresses of the changed object, the move module obtains the virtual volume name and the virtual volume address corresponding to the object name and the object address of the changed object, obtains the logical volume name and the logical volume address corresponding to the obtained virtual volume name and the virtual volume address, obtains one or more RAID group names and addresses corresponding to the obtained logical volume name and the logical volume address, selects from the one or more RAID group names and addresses a RAID group which has a least amount of assigned capacity, selects a logical volume for random access which is associated with the selected RAID group, and moves data from an area associated with the obtained logical volume name and the logical volume address of the changed object to the selected logical volume for random access. If the access type of the changed object is changed from a randomly accessed object to a sequentially accessed object, the move module selects a RAID group for which the access type is SEQUENTIAL, selects a logical volume for which a RAID group name is associated with the selected RAID group, obtains a source address of the changed object based on the object allocation information and on virtual volume information which correlates virtual volume name and address with logical volume name and address, and moves data from the source address to the selected logical volume. 
     In accordance with another aspect of this invention, a storage system comprises a processor; a memory; a disk control module configured to receive a write command for writing to an unallocated area and to identify a target volume for an object of the write command to be written as a written object; and an object allocation acquisition module configured to obtain object allocation information specifying one or more virtual volume locations for storing the written object. The disk control module allocates, to each of the one or more virtual volume locations, an area selected from a plurality of logical volumes if the target volume is predefined as a randomly accessed volume. The disk control module allocates to the one or more virtual volume locations a consecutive area of one logical volume if the target volume is predefined as a sequentially accessed volume. 
     In accordance with another aspect of the invention, a storage system comprises a processor; a memory; a disk control module configured to receive a write command for writing to an unallocated area, and to identify an object of the write command to be written as a written object or a target volume for an object of the write command to be written as a written object; and an object allocation acquisition module configured to obtain object allocation information specifying one or more virtual volume locations for storing the written object. If the disk control module identifies a written object of the write command, the disk control module allocates to the one or more virtual volume locations an area having portions selected from a plurality of logical volumes if the written object is predefined as a randomly accessed object, and allocates to the virtual volume location a consecutive area of one logical volume if the written object is predefined as a sequentially accessed object. If the disk control module identifies a written object of the write command, the disk control module allocates, to each of the one or more virtual volume locations, an area selected from a plurality of logical volumes if the written object is predefined as a randomly accessed object, and the disk control module allocates to the one or more virtual volume locations a consecutive area of one logical volume if the written object is predefined as a sequentially accessed object. If the disk control module identifies a target volume for a written object of the write command, the disk control module allocates, to each of the one or more virtual volume locations, an area selected from a plurality of logical volumes if the target volume is predefined as a randomly accessed volume, and the disk control module allocates to the one or more virtual volume locations a consecutive area of one logical volume if the target volume is predefined as a sequentially accessed volume. 
     In some embodiments, if the disk control module identifies a written object of the write command, then the disk control program is configured to obtain the one or more virtual volume locations for storing the written object from the object allocation information, obtain one or more logical volume locations corresponding to the obtained one or more virtual volume locations based on virtual volume information, and obtain one or more RAID group names and addresses corresponding to the obtained one or more logical volume locations based on logical volume information. 
     These and other features and advantages of the present invention will become apparent to those of ordinary skill in the art in view of the following detailed description of the specific embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a hardware configuration of an information system in which the method and apparatus of the invention may be applied 
         FIG. 2  illustrates an example of the memory in the application server and the memory in the storage subsystem of  FIG. 1 . 
         FIG. 3  illustrates an example of the object allocation information in the storage subsystem of  FIG. 1 , a read command, and a write command. 
         FIG. 4  shows an example of the RAID group information, the logical volume information, and the pool information. 
         FIG. 5  shows an example of the virtual volume information, the access type definition information, and the object assignment information according to the first embodiment. 
         FIG. 6  shows an example of an access type setting screen according to the first embodiment. 
         FIG. 7  shows an example of a diagram illustrating relationships between table and virtual volume, virtual volume and logical volume, and logical volume and RAID group. 
         FIG. 8  is an example of a flow diagram showing that the storage subsystem reads data from the SSD and the HDD, and writes data to the SSD and the HDD when the storage subsystem receives the read command or the write command from the application server. 
         FIG. 9  is an example of a flow diagram showing the disk control program allocates an area of a virtual volume to an unallocated area in step  804  of  FIG. 8  according to the first embodiment. 
         FIG. 10  is an example of a flow diagram showing a process when the access type definition information is changed using the access type setting screen. 
         FIG. 11  illustrates an example of the access type definition information, the object assignment information, and the access type setting screen according to the second embodiment. 
         FIG. 12  is an example of a flow diagram showing the disk control program allocates an area of a virtual volume to an unallocated area in step  804  of  FIG. 8  according to second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of the invention, reference is made to the accompanying drawings which form a part of the disclosure, and in which are shown by way of illustration, and not of limitation, exemplary embodiments by which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. Further, it should be noted that while the detailed description provides various exemplary embodiments, as described below and as illustrated in the drawings, the present invention is not limited to the embodiments described and illustrated herein, but can extend to other embodiments, as would be known or as would become known to those skilled in the art. Reference in the specification to “one embodiment,” “this embodiment,” or “these embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention, and the appearances of these phrases in various places in the specification are not necessarily all referring to the same embodiment. Additionally, in the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details may not all be needed to practice the present invention. In other circumstances, well-known structures, materials, circuits, processes and interfaces have not been described in detail, and/or may be illustrated in block diagram form, so as to not unnecessarily obscure the present invention. 
     Furthermore, some portions of the detailed description that follow are presented in terms of algorithms and symbolic representations of operations within a computer. These algorithmic descriptions and symbolic representations are the means used by those skilled in the data processing arts to most effectively convey the essence of their innovations to others skilled in the art. An algorithm is a series of defined steps leading to a desired end state or result. In the present invention, the steps carried out require physical manipulations of tangible quantities for achieving a tangible result. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals or instructions capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, instructions, or the like. It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise, as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” “displaying,” or the like, can include the actions and processes of a computer system or other information processing device that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system&#39;s memories or registers or other information storage, transmission or display devices. 
     The present invention also relates to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may include one or more general-purpose computers selectively activated or reconfigured by one or more computer programs. Such computer programs may be stored in a computer-readable storage medium, such as, but not limited to optical disks, magnetic disks, read-only memories, random access memories, solid state devices and drives, or any other types of media suitable for storing electronic information. The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs and modules in accordance with the teachings herein, or it may prove convenient to construct a more specialized apparatus to perform desired method steps. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. The instructions of the programming language(s) may be executed by one or more processing devices, e.g., central processing units (CPUs), processors, or controllers. 
     Exemplary embodiments of the invention, as will be described in greater detail below, provide apparatuses, methods and computer programs for the allocation of an area of logical volume to a virtual volume based on object access type. 
     First Embodiment: Object-Based Access Type Management System Configuration 
       FIG. 1  illustrates an example of a hardware configuration of an information system in which the method and apparatus of the invention may be applied. The system comprises an application server  100 , a SAN (Storage Area Network)  120 , a LAN (Local Area Network)  140 , and a storage subsystem  160 . The application server  100  comprises a CPU (Central Processing Unit)  101 , a memory  102 , a HDD (Hard Disk Drive)  103 , a SAN interface  104 , and a LAN interface  105 . The CPU  101  reads programs from the memory  102  and executes the programs. The memory  102  reads programs and data from the HDD  103  when the application server  100  starts and stores the programs and the data. The HDD  103  stores programs and data. The SAN interface  104  connects the application server  100  and the SAN  120 . The LAN interface  105  connects the application server  100  and the LAN  140 . The SAN  120  connects the application server  100  and the storage subsystem  160 . The application server  100  uses the SAN  120  to send application data to the storage subsystem  160  and receive application data from the storage subsystem  160 . The application server  100  uses the LAN  140  to send management data to the storage subsystem  160  and receive management data from the storage subsystem  160 . The LAN  140  connects the application server  100  and the storage subsystem  160 . The storage subsystem  160  comprises a SAN interface  161 , a LAN interface  162 , a CPU  163 , a memory  164 , a disk interface  165 , a SSD (Solid State Drive)  166 , and a HDD  167 . The SAN interface  161  connects the storage subsystem  160  and the SAN  120 . The LAN interface  162  connects the storage subsystem  160  and the LAN  140 . The CPU  163  reads programs from the memory  164  and executes the programs. The memory  164  reads programs and data from the HDD  167  and SSD  166  when the storage subsystem  160  starts and stores the programs and the data. The disk interface  165  connects the storage subsystem  160 , the SSD  166 , and the HDD  167 . The SSD  166  stores programs and data. The HDD  167  stores programs and data. 
       FIG. 2  illustrates an example of the memory  102  in the application server  100  and the memory  164  in the storage subsystem  160  of  FIG. 1 . The memory  102  comprises an OS (Operating System) program  201 , an application program  202 , and object allocation information  203 . The OS program  201  executes the application program  202 . The application program  202  (e.g., database program) reads data from the storage subsystem  160 , processes data, writes the results to the storage subsystem  160 , and manages the object allocation information  203 . The object allocation information  203  includes a location where an object is saved. 
     The memory  164  comprises a disk control program  221 , RAID (Redundant Arrays of Inexpensive (or Independent) Disks) group information  222 , logical volume information  223 , pool information  224 , virtual volume information  225 , access type definition information  226 , object assignment information or allocation information  227 , a move program  228 , and an object allocation acquisition program  229 . The disk control program  221  receives a read command and a write command from the application server  100 , reads data from the SSD  166  and the HDD  167 , and writes data to the SSD  166  and the HDD  167  using the RAID group information  222 , the logical volume information  223 , the pool information  224 , the virtual volume information  225 , and the access type definition information  226 . The move program  228  moves data to some other area. 
       FIG. 3  illustrates an example of the object allocation information  203  in the storage subsystem  160  of  FIG. 1 , a read command  340 , and a write command  360 . The object allocation information  203  of  FIG. 3  is a table and includes columns of an object name  301 , an object address  302 , a virtual volume name  303 , and a virtual volume address  304 . For example, the row  305  shows that the address from “0” to “99” in “TABLE A” is allocated to the address from “0” to “99” in “V-VOL A.” 
     The read command  340  includes a command type  341 , a volume name  342 , and a volume address  343 . The read command  340  is sent from the application program  202  to the disk control program  221 . The write command  360  includes a command type  361 , a volume name  362 , a volume address  363 , and data  364 . The write command  360  is sent from the application program  202  to disk control program  221 . 
       FIG. 4  shows an example of the RAID group information  222 , the logical volume information  223 , and the pool information  224 . 
     The RAID group information  222  includes columns of a RAID group name  401 , a media name  402 , a RAID level  403 , and an access type  404 . For example, the row  405  shows that “RG A” has “HDD A,” “HDD B,” “HDD C,” and “HDD D,” the RAID level of “RG A” is “RAID 5 (3D+1P),” and “RG A” is used for random access. 
     The logical volume information  223  includes columns of a logical volume name  421 , a logical volume address  422 , a RAID group name  423 , and a RAID group address  424 . For example, the row  425  shows that “L-VOL A” is allocated to the address from “0” to “999” in “RG A.” 
     The pool information  224  includes columns of a pool name  441 , a logical volume name for random access  442 , a logical volume name for sequential access  443 , and a virtual volume name  444 . For example, the row  445  shows “POOL A” has “L-VOL A”, “L-VOL B,” and “L-VOL C” for random access and “L-VOL D” and “L-VOL E” for sequential access, and the area of “POOL A” is used by “V-VOL A.” 
       FIG. 5  shows an example of the virtual volume information  225 , the access type definition information  226 , and the object assignment information  227  according to the first embodiment. 
     The virtual volume information  225  includes columns of a virtual volume name  501 , a virtual volume address  502 , a logical volume name  503 , and a logical volume address  504 . For example, the row  505  shows that the address from “0” to “99” in “V-VOL A” is allocated to the address from “0” to “99” in “L-VOL A.” 
     The access type definition information  226  includes columns of an object name  521  and an access type  522 . For example, the row  523  shows “TABLE A” is accessed randomly and the row  524  shows “TABLE B” is accessed sequentially. 
     The object assignment information  227  includes columns of an object name  541 , a RAID group name  542 , and assigned capacity  543 . The RAID group name  542  shows a list of RG names for which the access type  404  is only “RANDOM” in the RAID group information  222 . For example, the row  544  shows “TABLE A” is assigned with an area in “RG A” and the assigned capacity is 100 bytes. 
       FIG. 6  shows an example of an access type setting screen  600  according to the first embodiment. An administrator inputs an object name  601  and an access type  602 . The access type definition information  226  is updated to the data input by the administrator when the administrator pushes an “OK” button  621 . 
       FIG. 7  shows an example of a diagram illustrating relationships between table and virtual volume, virtual volume and logical volume, and logical volume and RAID group.  FIG. 7  shows TABLE A  701 , TABLE B  702 , V-VOL A  703 , L-VOL A  704 , L-VOL B  705 , L-VOL C  706 , L-VOL D  707 , RG A  708 , RG B  709 , RG C  710 , and RG D  711 . For example, the address “0” to “99” in the TABLE A  701  is mapped to the address “0” to “99” in the V-VOL A  703 , the address “0” to “99” in the V-VOL A  703  is mapped to the address “0” to “99” in the L-VOL A  704 , and the address “0” to “999” in the L-VOL A  704  is mapped to the address “0” to “999” in the RG A  708 .  FIG. 7  shows object assignment for randomly accessed object amongst L-VOL A and RG A, L-VOL B AND RG B, and L-VOL C and RG C.  FIG. 7  further shows object assignment for sequentially accessed object to L-VOL D and RG D. 
     Process Flows 
       FIG. 8  is an example of a flow diagram showing that the storage subsystem  160  reads data from the SSD  166  and the HDD  167 , and writes data to the SSD  166  and the HDD  167  when the storage subsystem  160  receives the read command  340  or the write command  360  from the application server  100 . 
     In step  801 , the disk control program  221  receives the read command  340  or the write command  360  from the application server  100 . In decision step  802 , if the command that the disk control program  221  received in step  801  is the write command  360 , then the process goes to decision step  803 ; if not, then the process goes to decision step  806 . In decision step  803 , if the volume name  362  and the volume address  363  are allocated in the virtual volume information  225 , then the process goes to step  805 ; if not, then the process goes to step  804 . 
     In step  804 , the disk control program  221  allocates an area and updates the virtual volume information  225 . In step  805 , the disk control program  221  gets the volume name  362  and the volume address  363  from the write command  360 , gets the logical volume name  503  and the logical volume address  504  from the virtual volume information  225 , gets the RAID group name  423  and the RAID group address  424  from the logical volume information  223 , gets the media name  402  from the RAID group information  222 , and writes the data  364  the SSD  166  and the HDD  167 . 
     In decision step  806 , if the volume name  342  and the volume address  343  are allocated in the virtual volume information  225 , then the process goes to step  808 ; if not, then the process goes to step  807 . In step  807 , the disk control program  221  returns “0” to the application server  100  because the area specified by the volume name  342  and the volume address  343  is not one to which data is written. In step  808 , the disk control program  221  gets the volume name  342  and the volume address  343  from the read command  340 , gets the logical volume name  503  and the logical volume address  504  from the virtual volume information  225 , gets the RAID group name  423  and the RAID group address  424  from the logical volume information  223 , gets the media name  402  from the RAID group information  222 , and reads data from the SSD  166  and the HDD  167 . 
       FIG. 9  is an example of a flow diagram showing the disk control program  221  allocates an area of a virtual volume to an unallocated area in step  804  of  FIG. 8  according to the first embodiment. 
     In step  901 , the object allocation acquisition program  229  gets the object allocation information  203  from the application server  100 . In step  902 , the disk control program  221  identifies the object to which the data  364  is written from the volume name  362 , the volume address  363 , and the object allocation information  203 . For example, the volume name  362  is “V-VOL A” and the volume address  363  is “300” to “399” and the area “300” to “399” of “L-VOL A” corresponds to the address “200” to “299” of “TABLE A.” Therefore, the data  364  is written to “TABLE A.” In step  903 , the disk control program  221  gets the access type  522  from the object name which is identified in step  902  and the access type definition information  226 . For example, the object name which is identified in step  902  is “TABLE A.” The access type  522  of “TABLE A” is “RANDOM” from the row  523  in the access type definition information  226 . In decision step  904 , if the access type  522  which the disk control program  221  gets in step  903  is “RANDOM,” then the process goes to step  905 ; if not, the process goes to step  908 . 
     In step  905 , the disk control program  221  selects a RAID group to allocate an area to a virtual volume. The disk control program  221  selects a RAID group that has the least amount of assigned capacity  543  among the objects associated with the object name  541  identified in step  902 . For example, when identified object name is “INDEX A” in step  902 , “RG C” is the least assigned capacity among “RG A,” “RG B,” and “RG C.” In step  906 , the disk control program  221  selects a logical volume to allocate an area to a virtual volume. The disk control program  221  selects the logical volume name  421  for the logical volume which is associated with the RAID group under the RAID group name  423  selected in step  905 . For example, when “RG C” is selected in step  905 , the disk control program  221  selects “L-VOL C.” In step  907 , the disk control program  221  allocates an area of the logical volume that is selected in step  906  to the virtual volume that is specified by the volume name  362  and the volume address  363 , and updates the virtual volume information  225 . 
     The selection of a RAID group that has the least amount of assigned capacity in step  905  ensures that data is written approximately evenly across the RAID groups and corresponding logical volumes. As such, the disk control program  221  allocates to the virtual volumes approximately evenly from the logical volumes. For a randomly accessed object to be stored in one or more virtual volume locations (i.e., a virtual volume name and one or more virtual volume addresses), the area to be allocated to each one of the virtual volume locations is selected from one of the logical volumes. Steps  905  to  907  are performed for each one of the virtual volume locations. 
     In step  908 , the disk control program  221  gets the object name  301  and the object address  302  from the write command  360  and the object allocation information  203 . For example, the volume name  362  is “V-VOL A” and the volume address  363  is “500” to “599,” and hence the object name  301  is “TABLE B” and the object address  302  is “200” to “299.” In step  909 , the disk control program  221  gets the adjacent previous address of the object address obtained in step  908 . For example, the object name obtained in step  908  is “TABLE B” and the object address obtained in step  908  is “200” to “299,” and thus the adjacent previous address is “100” to “199.” In decision step  910 , if the disk control program  221  finds the virtual volume name  303  and the virtual volume address  304  of the adjacent previous address, then the process goes to step  911 ; if not, the process goes to step  915 . In step  911 , the disk control program  221  gets the virtual volume name  303  and the virtual volume address  304  of the adjacent previous address obtained in step  909  from the object allocation information  203 . For example, the adjacent previous address obtained in step  909  is “100” to “199,” and hence the virtual volume name  303  is “V-VOL A” and the virtual volume address  304  is “400” to “499.” In step  912 , the disk control program  221  gets the logical volume name  503  and the logical volume address  504  allocated to the virtual volume and the virtual volume address obtained in step  911  from the virtual volume information  225 . For example, the virtual volume name  303  is “V-VOL A” and the virtual volume address  304  is “400” to “499” obtained in step  911 , and thus the logical volume name  503  is “L-VOL D” and the logical volume address  504  is “100” to “199.” In step  913 , the disk control program  221  gets the adjacent subsequent address of the logical volume address obtained in step  912 . For example, the logical volume name  503  is “L-VOL D” and the logical volume address  504  is “100” to “199” obtained in step  912 ; therefore, the subsequent address is “200” to “299.” In step  914 , the disk control program  221  allocates the area obtained in step  913  to the virtual volume specified by the volume name  362  and the volume address  363 . In step  915 , the disk control program  221  allocates an area of a logical volume of a RAID group that has the access type  404  of “SEQUENTIAL.” 
       FIG. 10  is an example of a flow diagram showing a process when the access type definition information  226  is changed using the access type setting screen  600 . In step  1001 , the move program  228  updates the access type definition information  226  with changed information from the access type setting screen  600 . In step  1002 , the move program  228  gets the object allocation information  203  from the application server  100 . In step  1003 , the move program  228  selects a changed object from the access type definition information  226 . In decision step  1004 , if the access type  522  of the object selected in step  1003  is changed from “SEQUENTIAL” to “RANDOM,” then the process goes to step  1005 ; if not, then the process goes to step  1010 . 
     In step  1005 , the move program  228  selects a row in which the object name  301  is for the object selected in step  1003  in the object allocation information  203 , selects a row in which the virtual volume name  501  and the virtual volume address are the same as the virtual volume name  303  and the virtual volume address  304  selected in this step, and gets the logical volume name  503  and the logical volume address  504  selected in this step from the virtual volume information  225 . For example, when the access type  522  of “TABLE B” is changed from “SEQUENTIAL” to “RANDOM,” the move program  228  selects the row  307  from the object allocation information  203 , selects the row  507  from the virtual volume information  225 , and gets the logical volume name  503  which is “L-VOL D” and the logical volume address  504  which is “0” to “99.” In step  1006 , the move program  228  selects a RAID group for random access. The move program  228  selects a RAID group that has the least amount of assigned capacity  543  among the objects associated with the object name  541  selected in step  1003 . For example, when the selected object name is “INDEX A” in step  1003 , “RG C” is the least assigned capacity among “RG A,” “RG B,” and “RG C.” In step  1007 , the move program  228  selects a logical volume for random access. The move program  228  selects the logical volume name  421  for which the RAID group name  423  is associated with the RAID group that is selected in step  1006 . For example, when “RG C” is selected in step  1006 , the disk control program  221  selects “L-VOL C.” In step  1008 , the move program  228  moves data from the area selected in step  1005  to the area selected in step  1007  and updates the virtual volume information  225 . In step  1009 , if the move program  228  moves the object selected in step  1003 , then the process goes to step  1013 ; if not, then the process goes to step  1005 . 
     In step  1010 , the move program  228  selects a RAID group for which the access type  404  is “SEQUENTIAL.” In step  1011 , the move program  228  selects a logical volume for which the RAID group name  423  is associated with the RAID group selected in step  1010 . In step  1012 , the move program  228  gets the source address of the object selected in step  1003  from the object allocation information  203  and the virtual volume information  225 , moves data from the source address to the logical volume selected in step  1011 , and updates the virtual volume information  225 . The process continues to step  1013 . 
     In decision step  1013 , if all changed objects are moved, then the process ends; if not, then the process goes to step  1003 . 
     Second Embodiment: Volume-Based Access Type Management 
     The following description of the second embodiment focuses on only the differences from the first embodiment. 
     System Configuration 
       FIG. 11  illustrates an example of the access type definition information  226 , the object assignment information  227 , and the access type setting screen  600  according to the second embodiment. 
     The access type definition information  226  includes columns of a virtual volume name  1101  and an access type  1102 . For example, the row  1103  shows “V-VOL A” is accessed randomly and the row  1104  shows “V-VOL B” is accessed sequentially. The object assignment information  227  includes columns of a virtual volume name  1121 , a RAID group name  1122 , and assigned capacity  1123 . The RAID group name  1122  shows a list of RG names for which the access type  404  is only “RANDOM” in the RAID group information  222 . For example, the row  1124  shows “V-VOL A” is assigned with an area in “RG A” and the assigned capacity is  100  bytes. An administrator inputs a virtual volume name  1141  and an access type  1142  on the access type setting screen  600 . The access type definition information  226  is updated to the data input by the administrator when the administrator pushes an “OK” button  1146 . 
     Process Flows 
       FIG. 12  is an example of a flow diagram showing the disk control program  221  allocates an area of a virtual volume to an unallocated area in step  804  of  FIG. 8  according to second embodiment. 
     In step  1202 , the disk control program  221  identifies the virtual volume to which the data  364  is written from the volume name  362 . In step  1203 , the disk control program  221  gets the access type  1102  from the virtual volume name which is identified in step  1202  and the access type definition information  226 . For example, the virtual volume name which is identified in step  1202  is “V-VOL A.” The access type  1102  of “V-VOL A” is “RANDOM” from the row  1103  in the access type definition information  226 . In decision step  1204 , if the access type  1102  which the disk control program  221  gets in step  1203  is “RANDOM”, then the process goes to step  1205 ; if not, the process goes to step  1209 . 
     In step  1205 , the disk control program  221  selects a RAID group to allocate an area to a virtual volume. The disk control program  221  selects a RAID group that has the least amount of assigned capacity  1123  among the objects associated with the virtual volume name  1121  identified in step  1202 . For example, when the identified object name is “V-VOL C” in step  1202 , “RG C” is the least assigned capacity among “RG A,” “RG B,” and “RG C.” In step  1206 , the disk control program  221  selects a logical volume to allocate an area to a virtual volume. The disk control program  221  selects the logical volume name  421  for which the RAID group name  423  is associated with the RAID group that is selected in step  1205 . For example, when “RG C” is selected in step  1205 , the disk control program  221  selects “L-VOL C.” In step  1207 , the disk control program  221  allocates an area of the logical volume that is selected in step  1206  to the virtual volume that is specified by the volume name  362  and the volume address  363 , and updates the virtual volume information  225 . 
     In step  1209 , the disk control program  221  gets the adjacent previous address of the object address specified by the write command  360 . For example, the volume name  362  is “V-VOL A” and the volume address  363  is “500” to “599,” and hence the adjacent previous address is “400” to “499.” In step  1212 , the disk control program  221  gets the logical volume name  503  and the logical volume address  504  allocated to the virtual volume and the virtual volume address obtained in step  1209  from the virtual volume information  225 . For example, the virtual volume name  501  obtained in step  1209  is “V-VOL A” and the virtual volume address  502  obtained in step  1212  is “400” to “499”, and thus the logical volume name  503  is “L-VOL D” and the logical volume address  504  is “100” to “199.” In step  1213 , the disk control program  221  gets the subsequent address of the logical volume address obtained in step  1212 . For example, the logical volume name  503  is “L-VOL D” and the logical volume address  504  is “100” to “199” obtained in step  1212 , and hence the adjacent subsequent address is “200” to “299.” In step  1214 , the disk control program  221  allocates the area obtained in step  1213  to the virtual volume specified by the volume name  362  and the volume address  363 . 
     Of course, the system configuration illustrated in  FIG. 1  is purely exemplary of information systems in which the present invention may be implemented, and the invention is not limited to a particular hardware configuration. The computers and storage systems implementing the invention can also have known I/O devices (e.g., CD and DVD drives, floppy disk drives, hard drives, etc.) which can store and read the modules, programs and data structures used to implement the above-described invention. These modules, programs and data structures can be encoded on such computer-readable media. For example, the data structures of the invention can be stored on computer-readable media independently of one or more computer-readable media on which reside the programs used in the invention. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include local area networks, wide area networks, e.g., the Internet, wireless networks, storage area networks, and the like. 
     In the description, numerous details are set forth for purposes of explanation in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that not all of these specific details are required in order to practice the present invention. It is also noted that the invention may be described as a process, which is usually depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. 
     As is known in the art, the operations described above can be performed by hardware, software, or some combination of software and hardware. Various aspects of embodiments of the invention may be implemented using circuits and logic devices (hardware), while other aspects may be implemented using instructions stored on a machine-readable medium (software), which if executed by a processor, would cause the processor to perform a method to carry out embodiments of the invention. Furthermore, some embodiments of the invention may be performed solely in hardware, whereas other embodiments may be performed solely in software. Moreover, the various functions described can be performed in a single unit, or can be spread across a number of components in any number of ways. When performed by software, the methods may be executed by a processor, such as a general purpose computer, based on instructions stored on a computer-readable medium. If desired, the instructions can be stored on the medium in a compressed and/or encrypted format. 
     From the foregoing, it will be apparent that the invention provides methods, apparatuses and programs stored on computer readable media for the allocation of an area of logical volume to a virtual volume. Additionally, while specific embodiments have been illustrated and described in this specification, those of ordinary skill in the art appreciate that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments disclosed. This disclosure is intended to cover any and all adaptations or variations of the present invention, and it is to be understood that the terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with the established doctrines of claim interpretation, along with the full range of equivalents to which such claims are entitled.