Patent Publication Number: US-8533415-B2

Title: Application migration and power consumption optimization in partitioned computer system

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation of application Ser. No. 12/339,271, filed Dec. 19, 2008 now U.S. Pat. No. 8,051,254; which relates to and claims priority from Japanese Patent Application No. 2008-269539, filed on Oct. 20, 2008, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to resource management in a computer system and, more specifically, to application migration and power supply control in a partitioned computer system. 
     DESCRIPTION OF THE RELATED ART 
     Considering the recent tendency of asking information processing systems to be environmentally friendly, proposed is the technology for implementing the efficient use of resources and the reduction of power consumption by consolidating computers and storage devices by virtualization. 
     Patent Document 1 (JP-A-2007-47986) describes the technology for load sharing by optimally placing any virtualized servers, virtualized switches, and virtualized storage devices in physical servers, physical switches, and physical storage devices. 
     Patent Document 2 (JP-A-2007-310791) describes the technology for consolidating, in a computer system including a plurality of physical servers, virtual servers into a few of the physical servers, thereby cutting off the power supply to the remaining physical servers. In the resulting computer system, the power consumption can be accordingly reduced. 
     Patent Document 3 (JP-A-2008-102667) describes the technology for cutting off the power supply to any not-in-use virtual computers and corresponding virtual storage devices through management of the correlation between the virtual computers and the virtual storage devices used thereby. In the resulting computer system, the power consumption can be accordingly reduced. 
     SUMMARY OF THE INVENTION 
     In a computer system partitioned based on any predetermined policy for use, applications are required to be run in any desired partition at any desired time. There thus sometimes needs to migrate virtual servers and logical volumes from one partition to another. Such migration consumes power, and to reduce the power consumption at the time of such migration, there needs to appropriately control the timing of migration. The problem here is that there has been no such technology. 
     A typical aspect of the invention is directed to a computer system that includes: one or more computers; one or more storage devices to be connected to the one or more computers over a network; and a management computer to be connected to the one or more computers and the one or more storage devices. In the computer system, characteristically, the one or more computers each include, as hardware resources: a first interface to be connected to the network; a first processor to be connected to the first interface; a first memory to be connected to the first processor; and a power supply control section that controls power ON and OFF of the hardware resources in accordance with a request coming from the management computer. The one or more computers each further include a virtualization section that provides a plurality of virtual areas based on the hardware resources thereof, the plurality of virtual areas include first and second virtual areas, and the first virtual area operates as a virtual computer that runs an application program. The one or more storage devices each include: a storage medium that provides a storage area for storage of data written by any of the one or more computers; a controller that controls data input/output to/from the storage medium; and a second power supply control section that controls power ON and OFF of each of the one or more storage devices in accordance with a request coming from the management computer. The controller of each of the one or more storage devices provides, to the one or more computers, the storage area of the one or more storage devices as a plurality of logical volumes, the plurality of logical volumes include first and second logical volumes, and the first logical volume stores data written by the virtual computer. The management computer includes: a second interface to be connected to the one or more computers and the one or more storage devices; a second processor to be connected to the second interface; and a second memory to be connected to the second processor. The management computer transmits, to any of the one or more storage devices including the first logical volume, a request for copying the data stored in the first logical volume into the second logical volume. The storage device including the first logical volume stores, when receiving a request for writing data to the first logical volume from the virtual computer after receiving the request for copying the data stored in the first logical volume into the second logical volume, the data requested for writing as differential data without writing the data into the first logical volume, and reads the data stored in the first logical volume in accordance with the request for copying the data stored in the first logical volume into the second logical volume, and transmits the data to any of the one or more storage devices including the second logical volume. The management computer transmits, when detecting completion of the copying of the data stored in the first logical volume into the second logical volume, a request to the storage device including the first logical volume for copying the differential data in storage into the second logical volume, transmits, in a time interval after detecting the completion of the copying of the data stored in the first logical volume into the second logical volume but before completion of the copying of the differential data into the second logical volume, a request for turning ON any of the hardware resources of the one or more computers allocated to the second virtual area to the computer including the hardware resources allocated to the second virtual area, and transmits, after the completion of the copying of the differential data into the second logical volume, a request for migrating the virtual computer to the second virtual area. The virtual computer performs, after being migrated to the second virtual area, data input/output to/from the second logical volume. 
     According to the aspect of the invention, the power to be consumed at the time of application migration can be favorably reduced through control of the timing of turning ON the resources at the time of application migration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a partition in an embodiment of the invention; 
         FIG. 2  is a block diagram showing the configuration of a computer system in the embodiment of the invention; 
         FIG. 3  is a diagram illustrating a first example of a physical partition in the embodiment of the invention; 
         FIG. 4  is a diagram illustrating a second example of the physical partition in the embodiment of the invention; 
         FIG. 5  is a diagram illustrating an exemplary logical partition in the embodiment of the invention; 
         FIG. 6  is a diagram illustrating the configuration of an application in the embodiment of the invention; 
         FIG. 7  is a diagram illustrating the system configuration in its entirety in the embodiment of the invention; 
         FIG. 8  is a flowchart of a partition-to-partition application migration process to be executed in the embodiment of the invention; 
         FIG. 9  is a diagram illustrating the detailed procedure of the partition-to-partition application migration process to be executed in the embodiment of the invention; 
         FIG. 10  is a detailed flowchart of the partition-to-partition application migration process to be executed in the embodiment of the invention; 
         FIG. 11  is a diagram illustrating logical volume migration to be performed in the embodiment of the invention; 
         FIG. 12  is a diagram illustrating another exemplary logical volume migration to be performed in the embodiment of the invention; 
         FIG. 13  is a diagram illustrating a third example of the physical partition in the embodiment of the invention; 
         FIG. 14  is a diagram illustrating application migration and power supply control to be performed in the embodiment of the invention; 
         FIG. 15  is a diagram illustrating a timing of application migration and power supply control to be performed in the embodiment of the invention; 
         FIGS. 16A and 16B  are each a diagram illustrating a management table in the embodiment of the invention; 
         FIG. 17  is an overall flowchart of an application migration process and a power supply control process to be executed in the embodiment of the invention; 
         FIG. 18  is a flowchart of a storage power-ON process to be executed in the embodiment of the invention; 
         FIG. 19  is a flowchart of a logical volume full copy process to be executed by a management server in the embodiment of the invention; 
         FIG. 20  is a flowchart of a logical volume full copy process to be executed by a storage device in the embodiment of the invention; 
         FIG. 21  is a flowchart of a server power-ON process to be executed in the embodiment of the invention; 
         FIG. 22  is a flowchart of an FC-SW power-ON process to be executed in the embodiment of the invention; 
         FIG. 23  is a flowchart of a logical volume differential copy process to be executed by the management server in the embodiment of the invention; 
         FIG. 24  is a flowchart of a logical volume differential copy process to be executed by the storage device in the embodiment of the invention; 
         FIG. 25  is a flowchart of a logical path migration process to be executed in the embodiment of the invention; 
         FIG. 26  is a flowchart of a virtual server migration process to be executed in the embodiment of the invention; 
         FIG. 27  is a flowchart of a migration-destination partition state check process to be executed in the embodiment of the invention; 
         FIGS. 28A and 28B  are each a diagram illustrating the management table after application migration in the embodiment of the invention; 
         FIG. 29  is a diagram illustrating a modified example of the application migration process and that of the power supply control process to be executed in the embodiment of the invention; 
         FIGS. 30A and 30B  are each a diagram illustrating the relationship between the size of the computer system and effects thereby in the embodiment of the invention; 
         FIG. 31  is a diagram illustrating a fourth example of the physical partition in the embodiment of the invention; and 
         FIG. 32  is a diagram illustrating a fifth example of the physical partition in the embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the invention is described in detail by referring to the accompanying drawings. 
       FIG. 1  is a diagram illustrating a partition in the embodiment of the invention. 
     The term of “partition” means an area being a defined result of partitioning an information system based on a user&#39;s business application type and a policy for use of the information system. The partitions are each acknowledged as a physical partition from a system design engineer, and as a logical partition from a user. 
     The physical partition means a physical area being a defined result of partitioning any physical resources. The system design engineer is allowed to determine the amount of physical resources for allocation to each partition. The amount of physical resources includes the number of cores of a CPU (Central Processing Unit), the capacity of a storage area of a memory, the zone size of a switch device configuring a network, the capacity of a storage area of a storage device, and others. 
     The logical partition means an area where a business application (application) is located. The user is allowed to determine which partition will be used for the application running, and a combination of a plurality of applications for the running in a partition. 
       FIG. 2  is a block diagram showing the configuration of a computer system in the embodiment of the invention. 
     The computer system of the embodiment is configured to include one or more storage devices  100 , one or more servers  120 , one or more fiber channel switches (FC-SW)  140 , a management server  130 , and a management network  150 . 
     The storage device  100  stores data written by the server  120 . To be specific, the storage device  100  is provided with disk drives  110 A to  110 C, and a controller  101 . 
     The disk drives  110 A to  110 C are each a memory device including a memory medium for storing data written by the server  120 . In the below, the disk drives  110 A to  110 C are sometimes collectively referred to as disk drives  110  when no distinction thereamong is needed. 
       FIG. 2  shows three of the disk drives  110 , but this is surely not restrictive, and the number of the disk drives  110  is not restrictive in the storage device  100 . Alternatively, a plurality of disk drives  110  may configure a RAID (Redundant Arrays of Inexpensive Disks). 
     The disk drives  110  in the embodiment are each a hard disk drive including a magnetic disk serving as a memory medium. This is surely not restrictive, and any type of device may be used as an alternative thereto. For example, the disk drives  110  may be each replaced by a nonvolatile semiconductor memory device such as flash memory. 
     The controller  101  controls data writing to the disk drives  110 , and data reading from the disk drives  110 . The controller  101  is configured to include a channel adaptor (CHA)  102 , a disk adaptor (DA)  103 , an interface (I/F)  104 , and a power supply control section  105 , which are connected to one another. 
     The CHA  102  is connected to any one port in the FC-SW  140 , e.g., port  141 B, and processes a data input/output (I/O) request from the server  120 , i.e., a data write request and a data read request. 
     The DA  103  is connected to the disk drives  110 , and controls data writing/reading to/from the disk drives  110 . 
     The CHA  102  and the DA  103  may respectively include a CPU (not shown) for execution of any requested process, and a local memory (not shown). 
     The I/F  104  is connected to the management network  150 , and communicates with the management server  130  over the management network  150 . 
     The power supply control section  105  controls power ON and OFF of the storage device  100 , i.e., controls start and stop of the power supply to the storage device  100 . More in detail, the power supply control section  105  controls the power supply to the components in the storage device  100  other than the power supply control section  105 . Such control is performed in accordance with control information provided by the management server  130  via the I/F  104 . Alternatively, the power supply control section  105  may perform such control over the power supply on a resource portion basis in the storage device  100 , e.g., on the basis of the disk drive  110 . Such a power supply control section  105  may be implemented by a so-called Baseboard Management controller (BMC), for example. 
     The controller  101  may further include a shared memory (not shown), and a cache memory (not shown). The shared memory stores therein various types of control information. The cache memory stores therein, on a temporary basis, data for writing into the disk drives  110 , and data read from the disk drives  110 . 
     The controller  101  manages a physical storage area as a plurality of logical volumes  111 . The physical storage area is the one implemented by a memory medium of the disk drive  110 . Logical volumes  111 A and  111 B of  FIG. 2  are each a part of the logical volumes  111 . The controller  101  can manage any arbitrary number of logical volumes  111 . 
     The computer system of this embodiment may include a plurality of storage devices  100 . 
     The server  120  is a computer configured to include a CPU  121 , a memory  122 , a power supply control section  123 , a host bus adaptor (HBA)  124 , an I/F  125 , and a virtualization section  129 , which are connected to one another. 
     The CPU  121  is a processor that serves to run a program stored in the memory  122 .  FIG. 2  shows only one CPU  121 , but the server  120  may include a plurality of CPUs  121 . 
     The memory  122  stores therein a program to be run by the CPU  121 , and data to be referred to by the CPU  121 . The memory  122  of this embodiment stores therein, at least, an operating system (OS)  128 , a path management program  127 , and an application program  126 . 
     The OS  128  is basic software for management use of the server(s)  120 , e.g., Windows™, or Unix™. As will be described later, a plurality of OSs  128  may be run on the server(s)  120 . If this is the case, the OSs  128  may be of a type or not. 
     The path management program  127  controls access paths from the server(s)  120  to the logical volumes  111 . 
     The application program  126  implements various types of business applications (applications). A user of the server  120  can install, to the server  120 , and run any of the application programs  126  that can implement his or her desired application. The application program  126  issues a data I/O request to the logical volumes  111  if needed. 
     Such software programs (programs) are each run by the CPU  121 . Accordingly, the processes to be executed by the above-described software programs (programs) in the below are actually executed by the CPU  121 . 
     The virtualization section  129  provides a plurality of virtual areas, i.e., virtual computers, using resources of the one or more servers  120  in the computer system, i.e., the CPU(s)  121 , the memory(ies)  122 , and others. The virtualization section  129  is allowed to make one server  120  to run a plurality of Oss  128 . Alternatively, the virtualization section  129  is allowed to implement so-called clustering, i.e., a plurality of servers  120  are used as a single virtual computer. 
     Such a virtualization section  129  may be a hardware resource mounted in the server  120 , or may be a program stored in the memory  122 , e.g., so-called virtual machine monitor or virtualization software such as hypervisor. When the virtualization section  129  is a program stored in the memory  122 , the virtualization section  129  is functioned by the CPU  121  running the virtualization software. 
     The HBA  124  is an interface communicating with the storage device  100  through connection to any of the ports in the FC-SW  140 , e.g., port  141 A. 
     The I/F  125  is connected with the management network  150 , and communicates with the management server  130  over the management network  150 . 
     The power supply control section 1   123  controls the power supply of the server  120 . To be specific, the power supply control section  123  controls power ON and OFF of the server  120  in accordance with control information provided by the management server  130  via the I/F  125 . The power supply control section  123  may be of a type similar to the power supply control section  105 . The power control section  123  may control power ON and OFF on a resource portion basis in the server  120 , e.g., when the server  120  includes a plurality of CPUs  121 , on the basis of the CPU  121 . 
     The CPU  121  runs the application program  126 , and if needed, forwards requests to the storage device  100  via the HBA  124 . The requests here are those for data writing and reading to/from the logical volumes  111 . The destination of such requests, in other words, the logical path for use with data I/O of these requests, is controlled by the path management program  127 . 
     The computer system of this embodiment may include a plurality of servers  120 . 
     The FC-SW  140  configures a network for relaying data I/O between the server  120  and the storage device  100 . The FC-SW  140  can change a data I/O path between the server  120  and the storage device  100 . In this embodiment, the data I/O between the serve  120  and the storage device  100  is exchanged based on the fiber channel (FC) protocol. 
     The FC-SW  140  is configured to include a plurality of ports  141 , e.g., ports  141 A to  141 D in  FIG. 2  example, an I/F  142 , and a power supply control section  143 . 
     The ports are each connected to the HBA  124  of the server  120 , or to the CHA  102  of the storage device  100 . 
     The FC-SW  140  can set a data communications path between the server  120  and the storage device  100  through connection settings among the ports  141 . The FC-SW  140  can also set so-called zones which are each independent. 
     The I/F  142  is connected to the management network  150 , and communicates with the management server  130  over the management network  150 . 
     The power supply control section  143  controls the power supply of the FC-SW  140 . To be specific, the power supply control section  143  controls power ON and OFF of the FC-SW  143  in accordance with control information provided by the management server  130  via the I/F  142 . The power supply control section  143  may be of a type similar to the power supply control section  105 . The power supply control section  143  may perform such control over power ON and OFF on a resource portion basis in the FC-SW  140 , e.g., on the basis of the port  141 . 
     The computer system of the embodiment may include a plurality of FC-SWs  140 . 
     The management server  130  is a computer configured to include a CPU  131 , a memory  132 , a database  133 , and an I/F  134 , which are connected to one another. 
     The CPU  131  is a processor that runs a program stored in the memory  132 . 
     The memory  132  stores therein a program to be run by the CPU  131 , and data to be referred to by the CPU  131 . The memory  132  of the embodiment stores therein at least a management program  135 . 
     The database  133  stores therein information for management use of the computer system. The database  133  may be stored in a disk drive connected to (or equipped) in the management server  130 . 
     The database  133  of this embodiment stores therein a management table  136 . If needed, the management table  136  may be entirely or partially copied into the memory  132 , and may be referred to by the CPU  131 . The contents of the management table  136  will be described later (refer to  FIGS. 16A and 16B ). 
     The I/F  134  is connected to the management network  150 , and communicates with the components, i.e., the storage device  100 , the server  120 , and the FC-SW  140 , over the management network  150 . For example, a signal for use to control the power supplies of the components, i.e., the storage device  100 , the server  120 , and the FC-SW  140 , is provided by the I/F  134  over the management network  150 . 
     The management network  150  may be of any type. Typically, the management network  150  is an IP (Internet Protocol) network such as so-called LAN (Local Area Network). If this is the case, the I/Fs  104 ,  125 , and  134  may be each a so-called network interface card. 
       FIG. 3  is a diagram illustrating a first example of the physical partition in the embodiment of the invention. 
       FIG. 3  shows an example in which three physical partitions, i.e., partitions  1 _ 300 A,  2 _ 300 B, and  3 _ 300 C, are defined. In this example, the partitions each include one or more servers  120 , one or more FC-SWs  140 , and one or more storage devices  100 . 
     To be specific, the partition  1 _ 300 A includes three servers  120 , three FC-SWs  140 , and three storage devices  100 . These three servers  120  form a cluster implemented by the virtualization section  129 . 
     Similarly, the partition  2 _ 300 B includes two servers  120 , two FC-SWs  140 , and two storage devices  100 . These two servers  120  form a cluster implemented by the virtualization section  129 . 
     The partition  3 _ 300 C includes one server  120 , one FC-SW  140 , and one storage device  100 . 
     Note that,  FIG. 3  shows no connection among the server(s)  120 , the FC-SW(s)  140 , and the storage device(s)  100 . 
     In the one or more servers  120  in each of the partitions, the OS  128  is run on the partition basis, and on the OS  128 , the application program  126  is run also on the partition basis. The application program  126  to be run on the partition basis as such performs data I/O to/from any logical volume in the one or more storage devices  100  in the partition via the one or more FC-SWs  140  therein. 
       FIG. 4  is a diagram illustrating a second example of the physical partition in the embodiment of the invention. 
       FIG. 4  shows an example in which three physical partitions, i.e., partitions  1 _ 300 D,  2 _ 300 E, and  3 _ 300 F, are defined in a computer system including one server  120 , one FC-SW  140 , and one storage device  100 . 
     To be specific, the server  120  of  FIG. 4  is provided with six of the CPUs  121 , and three thereof are allocated to the partition  1 _ 300 D, two thereof are allocated to the partition  2 _ 300 E, and one thereof is allocated to the partition  3 _ 300 F. 
     The FC-SW  140  of  FIG. 4  is provided with twelve of the ports  141 , and four thereof are allocated to the partition  1 _ 300 D, four out of the remaining eight are allocated to the partition  2 _ 300 E, and the remaining four are allocated to the partition  3 _ 300 F. The four ports  141  allocated to each of the partitions as such form a zone  401 . 
     As to the storage area provided by the storage device  100  of  FIG. 4 , a part thereof, e.g., partially a volume pool  402 , is allocated to the partition  1 _ 300 D, another part of the volume pool  402  is allocated to the partition  2 _ 300 E, and the remaining part of the volume pool  402  is allocated to the partition  3 _ 300 F. Note here that the volume pool  402  denotes a management unit of the storage area configured by one or more logical volumes  111 . 
     In such an example, in one or more CPUs  121  allocated to each of the partitions, the OS  128  is run on the partition basis, and on the OS  128 , the application program  126  is also run on the partition basis. The application program to be run on the partition basis as such performs data I/O to/from the storage area allocated to the partition. 
     As described above, the partition may be defined by coupling the resources of a plurality of devices (refer to  FIG. 3 ), or may be defined by dividing the resources of a device (refer to  FIG. 4 ). In either case, the system design engineer acknowledges the partitions as physical partitions as the results of partitioning any physical resources. 
       FIG. 5  is a diagram illustrating an exemplary logical partition in the embodiment of the invention. 
     A user of the computer system acknowledges a partition as an area where his or her running business application is located. In the description below, the “business application” is referred to as “application”. For example, the partitions of  FIG. 3 , i.e., the partitions  1 _ 300 A, the partition  2 _ 300 B, and the partition  3 _ 300 C, may be acknowledged by the user respectively as logical partitions, i.e., a partition  1 _ 300 G, a partition  2 _ 300 H, and a partition  3 _ 300 I. Alternatively, the partitions of  FIG. 4 , i.e., the partition  1 _ 300 D, the partition  2 _ 300 E, and the partition  3 _ 300 F, may be acknowledged by the user respectively as logical partitions, i.e., the partition  1 _ 300 G, the partition  2 _ 300 H, and the partition  3 _ 300 I. 
     In  FIG. 5  example, three business applications (applications)  500  are run in the partition  1 _ 300 G, two applications  500  are run in the partition  2 _ 300 H, and one application  500  is run in the partition  3 _ 300 I. 
       FIG. 6  is a diagram illustrating the configuration of the application  500  in the embodiment of the invention. 
     The application  500  of  FIG. 5  is configured by, as shown in  FIG. 6 , a virtual server (VM)  601 , a logical path  602 , and a logical volume (LU)  603 . 
     The virtual server  601  is a virtual computer implemented by the virtualization section  129 . 
     The logical path  602  is used by the virtual server  601  to access the logical volume  603 . The logical path  602  is implemented by any physical path reaching the storage device  100  from the HBA  124  via the FC-SW  140 . 
     The logical volume  603  is a logical storage area provided by the storage device  100  to the virtual server  601 . The virtual server  601  acknowledges one logical volume  603  as one storage device. For example, one logical volume  111  may be provided as one logical volume  603 , or a plurality of logical volumes  111  may be provided as one logical volume  603 . Alternatively, when a request comes for data writing to the storage area of the logical volume  603 , the storage area may be allocated with the storage area of the logical volume  111 . 
     The OS  128  is run on the virtual server  601 , and on the OS  128 , the application program  126  is run. The application program  126  performs data I/O to/from the logical volume  603  via the logical path  602 , thereby implementing the application  500 . 
     The applications  500  are each allowed to migrate from one partition to another. Such migration of the applications  500  will be described later. 
       FIG. 7  is a diagram illustrating the system configuration in its entirety in the embodiment of the invention. 
     The partitions of  FIG. 7 , i.e., the partitions  1 _ 300 A,  2 _ 300 B, and  3 _ 300 C, are acknowledged by a system manager as physical partitions similar to those of  FIG. 3 . 
     On the other hand, a user acknowledges the partitions  1 _ 300 A,  2 _ 300 B, and  3 _ 300 C as logical partitions. In the partition  1 _ 300 A, two applications (APP)  500 , i.e., applications  500 A and  500 B, are located, and in partition  2 _ 300 B, two applications  500 , i.e., applications  500 C and  500 D, are located. In the partition  3 _ 300 C, one application, i.e., application  500 E, is located. 
     The components configuring the application  500 A, i.e., the virtual server  601 , the logical path  602 , and the logical volume  603 , are referred to as virtual server  601 A, logical path  602 A, and logical volume  603 A, respectively. Similarly, the application  500 B is configured by a virtual server  601 B, a logical path  602 B, and a logical volume  603 B. The application  500 C is configured by a virtual server  601 C, a logical path  602 C, and a logical volume  603 C. The application  500 D is configured by a virtual server  601 D, a logical path  602 D, and a logical volume  603 D. The application  500 E is configured by a virtual server  601 E, a logical path  602 E, and a logical volume  603 E. 
     In the description below, the applications  500 A to  500 E are collectively referred to as applications  500  when no distinction thereamong is needed. The virtual servers  601 A to  601 E are collectively referred to as virtual servers  601  when no distinction thereamong is needed. The logical paths  602 A to  602 E are collectively referred to as logical paths  602  when no distinction thereamong is needed. The logical volumes  603 A to  603 E are collectively referred to as logical volumes  603  when no distinction thereamong is needed. 
     The management program  135  of the management server  130  manages the partitions. To be specific, the management server  130  manages the components in each of the partitions, i.e., the server  120 , the FC-SW  140 , and the storage device  100 , through connection thereto over the management network  150 . 
     The management program  135  also manages allocation of hardware resources to the partitions, and locating of the applications  500  in the partitions. For example, the management program  135  can control migration of the applications  500  from one partition to another, to be specific, migration of the logical volumes  603 , change of the logical paths  602 , and migration of the virtual servers  601 . 
     Described now is the migration of the applications  500  from one partition to another in the embodiment. 
     The management program  135  is allowed to migrate the applications  500  from one partition to another. Such application migration is performed for various types of purposes, e.g., for reduction of power consumption, or for load sharing. 
     To be specific, when the applications  500 A to  500 E of  FIG. 7  are hardly used at nighttime, for example, the applications  500  may be controllably migrated, e.g., the applications  500 A to  500 E may be located in a partition at nighttime and scattered among a plurality of partitions at daytime. For example, the applications  500  may be located as shown in  FIG. 7  at daytime, e.g., from 8:00 to 0:00 next day, and the applications  500 A to  500 E may be all located in the partition  3 _ 300 C at nighttime, e.g., 0:00 to 8:00. 
     In this case, the management program  135  takes charge of the process of migrating the applications  500 A and  500 B from the partition  1 _ 300 A to  3 _ 300 C at 0:00, and the process of migrating the applications  500 C and  500 D from the partition  2 _ 300 B to  3 _ 300 C also at 0:00. Thereafter, the partitions  1 _ 300 A and  2 _ 300 B are both turned OFF, i.e., cut off the power supply to the physical resources allocated to these partitions, thereby favorably reducing the power consumption of the computer system. 
     The management program  135  then takes charge of the process of migrating the applications  500 A and  500 B from the partition  3 _ 300 C to  1 _ 300 A at 8:00, and the process of migrating the applications  500 C and  500 D from the partition  3 _ 300 C to  2 _ 300 B also at 8:00. After the application migration at 0:00, when the partitions each being the migration destination are being turned OFF, there needs to turn on the partitions before application migration at 8:00 is started. 
       FIG. 8  is a flowchart of a partition-to-partition migration process for the application  500  to be performed in the embodiment of the invention. 
     The management program  135  starts the migration process for the application  500  at any specific time being a trigger, for example (step  801 ). In  FIG. 7  example above, the migration process may be started at 0:00 and 8:00, for example. Alternatively, the migration process may be started at the time being the result of subtracting the time needed for the end process from 0:00 and 8:00. If this is the case, the migration process is ended at 0:00 and 8:00. 
     The management program  135  then checks in which partition the application  500  being a migration target is currently located (step  802 ). For such checking, the management table  136  that will be described later is referred to. 
     The management program  135  then selects any of the partitions as a migration destination (step  803 ). When the partition being a migration destination is already determined as in  FIG. 7  example, the partition may be selected. When there are a plurality of partitions that can be selected as a migration destination, any one of those may be selected. 
     The management program  135  then checks the state of the partition selected as a migration destination (step  804 ). To be specific, the management program  135  refers to information about the number of the applications  500  already located in the partition selected as a migration destination, the capacity of the logical volume(s)  603  being already used by the application(s)  500 , and a time range in which the partition is available for use, for example. The process executed in step  804  will be described in more detail later by referring to  FIG. 27 . 
     The management program  135  then determines whether the application  500  can be migrated to the selected partition based on the information referred to in step  804  (step  805 ). For reference in step  804  and for determination in step  805 , the management table  136  is referred to. 
     In step  805 , when the determination result tells that no migration is allowed for the application  500  to the selected partition, the procedure returns to step  803 , and the management program  135  selects another partition as a migration destination. Note here that when the determination result tells that no application migration is allowed to all of the partitions that can be selected, the management program  135  may end the process of  FIG. 8  without performing migration of the application  500 . 
     In step  805 , when the determination result tells that migration is allowed for the application  500  to the selected partition, the management program  135  performs the migration of the application  500  (step  806 ). This migration will be described in detail later by referring to  FIGS. 9 and 10 . 
     The management program  135  then updates information about the location of the application  500  to reflect the migration in step  806  (step  807 ). This information is specifically the one included in the management table  136 . This update will be described in detail later by referring to the management table  136 . 
     This is the end of the migration process for the application  500  (step  808 ). 
       FIG. 9  is a diagram illustrating the detailed procedure of the partition-to-partition migration process for the application  500  to be performed in the embodiment of the invention. 
       FIG. 9  shows, as an example, in the computer system of  FIG. 7 , the procedure of moving the application  500 A from the partition  1 _ 300 A to the partition  2 _ 300 B. Herein, for the sake of simplicity, any not-necessary component is not shown. 
     In  FIG. 9 , A shows the initial state, i.e., the state before migration of the application  500 A. In this state, the virtual server  601 A is operating in the server  120  in the partition  1 _ 300 A. The logical volume  603 A is managed by the storage device  100  in the partition  1 _ 300 A. The logical path  602 A that is used by the virtual server  601 A to access the logical volume  603 A goes via the FC-SW  140  in the partition  1 _ 300 A. 
     In such a state, when migration of the application  500 A is started, first of all, migration of the logical volume  603 A is accordingly started. To be specific, a replica of the logical volume  603 A is created in the storage device  100  in the partition  2 _ 300 B. 
     In  FIG. 9 , B shows the state after completion of the migration of the logical volume  603 A. A logical volume  603 F in B of  FIG. 9  is the replica of the logical volume  603 A. For creating such a replica, executed is a process of reading every data stored in the logical volume  603 A, and copying the data into the logical volume  603 F. In the state of B of  FIG. 9 , such data copying is completed but the virtual server  601 A remains to access the logical volume  603 A, and thus the logical volume  603 F is not yet used. 
     Thereafter, migration of the logical path  602 A is performed. To be specific, the logical path  602 A is changed in setting to be able to access the logical volume  603 F by going via the FC-SW  140  in the partition  2 _ 300 B. This setting change may be made by the path management program  127  of the server  120  in the partition  1 _ 300 A newly acknowledging the logical volume  603 F as the logical volume  603 A, and by a transmission destination of a data I/O request to the logical volume  603 A being changed from the port  141  of the FC-SW  140  in the partition  1 _ 300 A to the port  141  of the FC-SW  140  in the partition  2 _ 300 B. 
     In  FIG. 9 , C shows the state after completion of the migration of the logical path  602 A. In this state, the logical path  602 A is so set that the virtual server  601 A in the partition  1 _ 300 A can access the logical volume  603 F by going via the FC-SW  140  in the partition  2 _ 300 B. 
     Thereafter, performed is migration of the virtual server  601 A. This migration is performed by copying an image of the memory  122  of the server  120  in the partition  1 _ 300 A into the memory  122  of the server  120  in the partition  2 _ 300 B, for example. Such migration may be implemented by the function of the virtualization section  129 . 
     In  FIG. 9 , D shows the state after completion of the migration of the virtual server  601 A. In this state, the virtual server  601 A having been migrated to the server  120  in the partition  2 _ 300 B can perform data I/O to/from the logical volume  603 F, i.e., new logical volume  603 A, using the logical path  602 A going via the FC-SW  140  in the partition  2 _ 300 B. This accordingly migrates the application  500 A to the partition  2 _ 300 B. 
     As will be described later, the migration of the logical volume  603 A can be performed without stopping the operation of the application  500 A. On the other hand, for migration of the logical path  602 A and the virtual server  601 A, there needs to stop the operation of the application  500 A. However, the time required for such operation stop is sufficiently short so that the application  500 A can be migrated without impairing user convenience. 
       FIG. 10  is a flowchart showing the detailed procedure of the partition-to-partition migration process for the application  500  to be executed in the embodiment of the invention. 
     The migration process of  FIG. 10  is started in step  806  of  FIG. 8  (step  1001 ). That is, when the process is started, the partition being a migration destination is already selected. Information for use to identify the selected partition is provided as an argument. 
     The management program  135  then starts migrating the application  500  to the selected partition (step  1002 ). To be specific, as shown in  FIG. 9 , the management program  135  first migrates the logical volume  603 , then the logical path  602 , and lastly the virtual server  601 . The process of step  1002  will be described in detail later by referring to  FIG. 17  and others. 
     The management program  135  then updates the management table  136  to reflect the migration result (step  1003 ). 
     This is the end of the migration process of  FIG. 10  (step  1004 ). Thereafter, the procedure returns to the flowchart of  FIG. 8 , and the process of step  807  and onwards is repeated. 
     Described next is the detailed procedure for migration of the logical volume  603 . 
       FIG. 11  is a diagram illustrating migration of the logical volume  603  to be performed in the embodiment of the invention. 
     As described above, migration of the logical volume  603  is performed without stopping the operation of the application  500 . Accordingly, there may be a case where, until data copying started for migration of the logical volume  603  is completed, data I/O may be started to/from the logical volume currently on the move. In this embodiment, the data I/O after the data copying is started is not reflected to the logical volume  603  but is stored as a differential stock. After completion of copying of data entirely in the logical volume  603 , the data I/O having been stored as a differential stock is reflected to the logical volume  603  being a copy destination. 
     As an example, as shown in  FIG. 9 , described is a casewhere the data in the logical volume  603 A is copied into the logical volume  603 F. Upon reception of a request for data writing into the logical volume  603 A after data copying is started, the controller  101  of the storage device  100  stores the data as a differential stock without writing it into the logical volume  603 A or  603 F. This differential stock may be stored in any of the logical volumes  111  in the storage device  100 , for example. 
     After completion of copying of the entire data stored in the logical volume  603 A into the logical volume  603 F (hereinafter, such copying is referred to as full copy), the data having been stored as a differential stock is then written into the logical volume  603 F. Such writing of data stored as a differential stock into a copy destination is hereinafter referred to as differential copy. 
     Such full copy and differential copy are controlled by the controller  101 . Alternatively, the full copy and the differential copy may be implemented by a control processor (not shown) in the controller  101  running an I/O control program (not shown) stored in a control memory (not shown), for example. 
     In this embodiment, in response to completion of a process of full copy, the server  120  and the FC-SW  140  are both turned ON. This is aimed to reduce the power consumption in the computer system. The timing control over power ON will be described in detail later (refer to  FIGS. 14 ,  15 , and others). 
     Note that, in the storage device of a previous type, the full copy and the differential copy are both dealt with as a single copy process, and thus any device located outside of the storage device, e.g., management server, had no way of knowing the timing when only the full copy is completed. Therefore, no control has been allowed to perform with a correlation between the completion of the full copy process (or the start of the differential copy process) and any other processes. On the other hand, in this embodiment, for favorably implementing the control as above, the storage device  100  may forward a message of completion of the full copy process to the management server  130  (refer to  FIG. 20  that will be described later), or the management server  130  may calculate the end time of the full copy process. 
       FIG. 12  is a diagram illustrating another exemplary migration of the logical volume  603  to be performed in the embodiment of the invention. 
     When the storage device  100  is provided with a volume copy function, i.e., so-called remote copy function or local copy function, the logical volume  603  can be migrated using the volume copy function. 
     Assuming that when a volume pair is configured by the logical volume  603 A being a primary volume and the logical volume  603 F being a secondary volume, updating of the data stored in the logical volume  603 A is reflected also to the logical volume  603 F. 
     When the setting is so made that updating of the logical volume  603 A is immediately reflected to the logical volume  603 F, the logical volume  603 F stores almost always the same data as in the logical volume  603 A. Accordingly, the time needed for migration of the logical volume  603 A for migration of the application  500 A as in  FIG. 9  is almost 0. 
     On the other hand, there may be a case where the setting is so made that updating of the logical volume  603 A is not immediately reflected to the logical volume  603 F. Alternatively, the setting may be so made that such updating is reflected at regular time intervals or reflected when the traffic amount of a data transfer path between the logical volumes  603 A and  603 F is smaller than a threshold value. If this is the case, during migration of the logical volume  603 A for migration of the application  500 A as in  FIG. 9 , only data of the logical volume  603 A updated after reflection as above, i.e., differential data, is copied. 
     When the application  500 A is located in the partition  1 _ 300 A, the logical volume  603 A is used, and when the application  500 A is located in the partition  2 _ 300 B, the logical volume  603 F is used. 
     As described above, by using the volume copy function, the logical volume  603  can be migrated in a shorter time compared with the case of performing the full copy and the differential copy as in  FIG. 11 . 
       FIG. 13  is a diagram illustrating a third example of the physical partition in the embodiment of the invention. 
     In  FIG. 13  example, similarly to  FIG. 3 , one or more servers  120  are allocated to each of the partitions, and similarly to  FIG. 4 , one FC-SW  140  and one storage device  100  are shared for use by a plurality of partitions. 
     Even with such a configuration, if the FC-SW  140  and the storage device  100  are allowed to control the power supply on a portion basis, the power supply control similar to the above can be performed. For example, when the storage device  100  is provided with a plurality of disk drives  110 , and is allowed to control power ON and OFF on the basis of the disk drive  110  (or on the basis of the RAID group configured by a plurality of disk drives (not shown), the power consumption can be favorably reduced as will be described later through control, at any appropriate timing, over the power supply of the disk drive  110  storing the logical volume  603  being a migration source, and over the power supply of the disk drive  110  including the logical volume  603  being a migration destination. 
     However, the reduction level of the power consumption as a result of the above-described portion-basis control by the storage device  100  or others is too small considering the power consumption of the computer system in its entirety, the effects of the reduction of power consumption by such portion-basis control are small. If this is the case, the devices shared for use by a plurality of partitions, e.g., the storage device  100 , may remain turned ON, and the server  120  may be controlled in terms of power supply. 
       FIG. 14  is a diagram illustrating migration of the application  500  and power supply control to be performed in the embodiment of the invention. 
       FIG. 14  shows, in addition to the procedure for migration of the application  500  described by referring to  FIG. 9 , the procedure for power supply control to be performed during the application migration. Note here that  FIG. 9  shows the example of migrating the application  500  from the partition  1 _ 300 A to the partition  2 _ 300 B, but  FIG. 14  shows an example of migrating the application  500  from the partition  2 _ 300 B to the partition  1 _ 300 A. For example, the process of  FIG. 14  is executed when the application  500 A migrated to the partition  2 _ 300 B as a result of the process of  FIG. 9  is put back to the partition  1 _ 300 A. Herein, also when the process of  FIG. 9  is executed, the power supply control similar to  FIG. 14  may be performed. 
     In  FIG. 14 , the hardware configuration such as the server  120  and the application configuration such as the virtual server  601 A are the same as those in  FIG. 9 , and thus are not described again. Note that, however,  FIG. 14  additionally show hardware identifiers, i.e., “server P 1 ”, “FC-SW P 1 ”, and “storage P 1 ” respectively for the server  120 , the FC-SW  140 , and the storage device  100  in the partition  1 _ 300 A, and “server P 2 ”, “FC-SW P 2 ”, and “storage P 2 ” respectively for the server  120 , the FC-SW  140 , and the storage device  100  in the partition  2 _ 300 B. These identifiers are registered in a table that will be described later (refer to  FIGS. 16A ,  16 B, and others). 
     At the time immediately before the process execution of  FIG. 14 , the components allocated to the partition  1 _ 300 A, i.e., the server  120 , the FC-SW  140 , and the storage device  100 , are being turned OFF. 
     In  FIG. 14  example, first of all, the storage device  100  is turned ON in the partition  1 _ 300 A being a migration destination. 
     For migration of the logical volume  603  from the partition  2 _ 300 B to the partition  1 _ 300 A, the full copy is then started. In  FIG. 14  example, the data stored in the logical volume  603 F is entirely copied into the logical volume  603 A. This copying is performed similarly to  FIG. 11 . That is, after full copy is started as such, updating of the logical volume  603 F is prohibited, and the update details are stored as a differential stock. 
     The full copy is then ended. 
     In response to completion of the full copy, in the partition  1 _ 300 A, the server  120  and the FC-SW  140  are both turned ON. In this embodiment, there needs to migrate the logical path  602 A before migration of the virtual server  601 A, and thus the server  120  is not required to be through with an activation process before an activation process of the FC-SW  140 . In consideration thereof, the FC-SW  140  may be turned ON first before the server  120  is turned ON. However, because the time needed to activate the server  120  is generally longer to activate the FC-SW  140 , the server  120  may be turned ON first as shown in  FIG. 14 . 
     Thereafter, differential copy is performed from the logical volume  603 F to  603 A. To be specific, the data stored as a differential stock is written into the logical volume  603 A. 
     Such migration of the logical volume  603  as above is implemented by the previous on-line migration function, for example. 
     After completion of the differential copy, the logical path  602 A is migrated to the partition  1 _ 300 A, and then the virtual server  601 A is migrated to the partition  1 _ 300 A. 
       FIG. 15  is a diagram illustrating migration of the application  500 , and the timing for power supply control to be performed in the embodiment of the invention. 
     To be specific,  FIG. 15  shows the execution timing for the processes of  FIG. 14 , and the time taken for execution thereof. In  FIG. 15 , the starting point of a one-way arrow (the left end of an arrow in  FIG. 15  example), the tip thereof (the right end of the arrow in  FIG. 15  example), and the length thereof are respectively corresponding to the starting time of the processes, the end time thereof, and the processing time thereof. 
     For example, an arrow  1501  denotes an activation process of the storage device  100 . The starting point of the arrow  1501  denotes the time when the storage device  100  is turned ON (time  1511 ), and the tip of the arrow  1501  denotes the time when the activation process of the storage device  100  is ended (time  1512 ). Similarly, an arrow  1502  denotes the full copy process of the logical volume  603 F, an arrow  1503  denotes the differential copy process of the logical volume  603 F, an arrow  1504  denotes an activation process of the server  120 , an arrow  1505  denotes an activation process of the FC-SW  140 , an arrow  1506  denotes a migration process of the logical path  602 A, and an arrow  1507  denotes a migration process of the virtual server  601 A. 
     As shown also in  FIG. 14 , the storage device  100  is turned ON first (time  1511 ), and after the storage device  100  is activated (time  1512 ), the full copy is started for the logical volume  603 F. Although being dependent on the amount of data stored in the logical volume  603 F, and the transfer performance of a data transfer path to be used for the copying, the time needed for the full copy is generally often sufficiently longer than the time needed for hardware activation and the time needed for differential copy. 
     In response to completion of the full copy (time  1513 ), the server  120  and the FC-SW  140  are both turned ON, and the differential copy is started for the logical volume  603 F. 
     After activation of the server  120  and the FC-SW  140 , and after completion of the differential copy (time  1514 ), migration of the logical path  602 A is started. After completion of the migration of the logical path  602 A (time  1515 ), migration of the virtual server  601 A is started. 
     Previously, the full copy process and the differential copy process are both dealt with as a single copy process, and thus the management server  130  had no way of knowing the end time of the full copy process, i.e., time  1513 . Therefore, no control has been allowed to perform in response to completion of full copy. In consideration thereof, in the embodiment, the time  1511  or  1514  can be used as control criteria, for example. 
     When the server  120  and the FC-SW  140  are both turned ON at the time  1511 , the arrows  1504  and  1505  of  FIG. 15  are so moved that their starting points come at the time  1511 . If this is the case, however, because the logical path  602 A and the virtual server  601 A are both allowed to migrate after the time  1514 , the server  120  and the FC-SW  140  have to wait idle but consume power until the time  1514  comes after being activated. That is, until the time  1514 , the server  120  and the FC-SW  140  waste power. 
     On the other hand, when the server  120  and the FC-SW  140  are both turned ON at the time  1514 , i.e., the end time of the differential copy, the arrows  1506  and  1507  of  FIG. 15  are moved to the later time, i.e., toward the right side. In this case, until the activation process is through for the server  120  and the FC-SW  140 , the logical path  602 A and the virtual server  601 A cannot be migrated. As a result, the time until completion of the migration of the application  500 A after the storage device  100  is turned ON becomes longer than the time in  FIG. 15  example. That is, in the time interval until the activation process is through for the server  120  and the FC-SW  140  after the completion of the differential copy process, the storage device  100  wastes power. 
     For minimizing the amount of power consumption of the computer system in its entirety, it is desirable to control power ON of the server  120  and the FC-SW  140  in such a manner that various processes are to be completed at the same time, i.e., the differential copy process, the activation process for the server  120 , and the activation process for the FC-SW  140 , that is, in such a manner that the tips of the arrows  1503 ,  1504 , and  1505  come at the same time. However, as described above, correctly estimating the time needed for the differential copy process is difficult. In consideration thereof, in this embodiment, the server  120  and the FC-SW  140  are both turned ON in response to completion of the full copy process. 
     If the data stored as a differential stock is large in amount, as shown in  FIG. 15 , the differential copy may not be completed even after activation of the server  120  and the FC-SW  140 . If this is the case, in the time interval until the differential copy is completed after activation of the server  120  and the FC-SW  140 , the server  120  and the FC-SW  140  waste power. On the other hand, when the data stored as a differential stock is small in amount, the differential copy may be completed even before activation of the server  120  and the FC-SW  140 . If this is the case, in the time interval until the server  120  and the FC-SW  140  are activated after completion of the differential copy, the storage device  100  wastes power. 
     As such, the end time of the full copy process is not always strictly optimal as the timing of turning ON the server  120  and the FC-SW  140 . However, generally, the migration time for the logical volume  603 , i.e., sum of the time needed for the full copy and the time needed for the differential copy, is generally much longer than the time needed for the activation process for the server  120  and the FC-SW  140 . As such, the optimal time for turning ON the server  120  and the FC-SW  140  is often just moments before the end time of the migration process for the logical volume  603 . On the other hand, the time needed for the full copy process is much longer than the time needed for the differential copy process, and thus the end time of the while copying process is often very close to the end time of the migration process for the logical volume  603 . Accordingly, the end time of the full copy process (time  1513 ) can be used as an approximately-optimal time for turning ON the server  120  and the FC-SW  140 . 
     In comparison with the case when the server  120  and the FC-SW  140  are both turned ON at the same time as the storage device  100 , and when the server  120  and the FC-SW  140  are both turned ON after the completion of the differential copy process, the power consumption can be successfully reduced in the computer system by turning ON the server  120  and the FC-SW  140  in response to the completion of the full copy process, specifically, after the completion of the full copy process but before the completion of the differential copy process. 
     Such a migration process for the application  500  is described in more detail. 
       FIGS. 16A and 16B  are each a diagram illustrating the management table  136  in the embodiment of the invention. 
     The management table  136  of the embodiment includes a partition management table  136 A, and an application management table  136 B. For the sake of simplicity,  FIGS. 16A and 16B  respectively show the partition management table  136 A and the application management table  136 B before migration of the application  500 A in  FIG. 14  example. 
       FIG. 16A  is a diagram illustrating the partition management table  136 A. The partition management table  136 A includes information for management use of the partitions defined on the computer system under the management of the management server  130 . 
     To be specific, the partition management table  136 A includes elements of “partition number  1601 ”, “hardware type  1602 ”, “hardware name  1603 ”, “resource amount  1604 ”, “remaining resource amount  1605 ”, “power supply  1606 ”, “located application (APP)  1607 ”, and “application resource amount  1608 ”. 
     The element of “partition number  1601 ” is information for use to identify each of the partitions defined on the computer system. In  FIG. 16A  example, the element of “partition number  1601 ” stores “1” and “2”. In this example, “1” denotes the identifier of the partition  1 _ 300 A, and “2” denotes the identifier of the partition  2 _ 300 B. 
     The element of “hardware type  1602 ” is information for use to identify the type of hardware resources allocated to each of the partitions. To be specific, the element of “hardware type  1602 ” is information for use to identify which of the server  120 , the FC-SW  140 , or the storage device  100  is the hardware resources allocated to each of the partitions. 
     In  FIG. 16A  example, “server  1 ”, “FC-SW  1 ”, and “storage  1 ” respectively denote the server  120 , the FC-SW  140 , and the storage device  100  in the partition  1 _ 300 A. On the other hand, “server  2 ”, “FC-SW  2 ”, and “storage  2 ” respectively denote the server  120 , the FC-SW  140 , and the storage device  100  in the partition  2 _ 300 B. 
     The element of “hardware name  1603 ” is information for use to identify the hardware resources allocated to each of the partitions. In  FIG. 16A  example, the element of “hardware name  1603 ” stores, for the partition  1 _ 300 A, “server P 1 ” (entry  1611 ), “FC-SW P 1 ” (entry  1612 ), and “storage P 1 ” (entry  1613 ). In this example, the “server P 1 ”, the “FC-SW P 1 ”, and the “storage P 1 ” are respectively identifiers of the server  120 , the FC-SW  140 , and the storage  100  all allocated to the partition  1 _ 300 A. 
     Also in  FIG. 16A  example, the element of “hardware name  1603 ” stores, for the partition  2 _ 300 B, “server P 2 ” (entry  1614 ), “FC-SW P 2 ” (entry  1615 ), and “storage P 2 ” (entry  1616 ). In this example, the “server P 2 ”, the “FC-SW P 2 ”, and the “storage P 2 ” are respectively identifiers of the server  120 , the FC-SW  140 , and the storage  100  all allocated to the partition  2 _ 300 B. 
     In  FIG. 16A  example, for consistency with the diagram of  FIG. 14 , one partition is allocated with one server  120 , one FC-SW  140 , and one storage device  100 . However, for actual use, one partition may be allocated with a plurality of servers  120 , a plurality of FC-SWs  140 , and a plurality of storage devices  100 . If this is the case, the element of “hardware name  1603 ” stores the identifiers of such a plurality of hardware resources. 
     Assuming that the partition  1 _ 300 A is allocated with two servers  120  having the identifiers of “server P 1 ” and “server P 10 ” (not shown), respectively, the “server  1 ” in the element of “hardware type  1602 ” is correlated with two entries, and for these entries, the element of “hardware name  1603 ” respectively store “server P 1 ” and “server P 10 ”. 
     The element of “resource amount  1604 ” indicates the entire amount of resources in each of the hardware resources. The measurement method for the resources is not restrictive. For example, the resource amount of the server  120  may be the number of the CPUs  121  provided to the server  120 , or may be the use rate of the CPU(s)  121 . The resource amount of the FC-SW  140  may be the number of the ports  141  provided thereto, or may be the number of the logical paths  602  available for connection therewith. The resource amount of the storage device  100  may be the storage capacity that can be provided as the logical volume(s)  111 . 
     In  FIG. 16A  example, the element of “resource amount  1604 ” stores “10” for each of the hardware resources.  FIG. 16A  example does not show the unit, but for actual use, may explicitly show the unit for each of the resource amounts, e.g., “terabytes” for the resource amount of the storage device  100 . 
     The element of “remaining resource amount  1605 ” indicates the amount of resources of each of the hardware resources not yet allocated to any of the applications  500 . In other words, the element of “remaining resource amount  1605 ” indicates the amount of resources being a result of subtracting the amount of resources having been allocated to any of the applications  500  from the amount of resources of each of the hardware resources. 
     The element of “power supply  1606 ” is information indicating the state of power supply in each of the hardware resources. In  FIG. 16A  example, “ON” in the element of “power supply  1606 ” indicates the state of power ON, and “OFF” therein indicates the state of power OFF. 
     The element of “located application  1607 ” is information for use to identify the application  500  located in each of the partitions. 
     The element of “application resource amount  1608 ” indicates the amount of resources having been allocated to the application  500  in each of the hardware resources. 
     The time frame of  FIG. 16A  example is, in  FIG. 14 , before the application  500 A is migrated from the partition  2 _ 300 B to the partition  1 _ 300 A. That is, at the point in time, the resources of each of the hardware resources in the partition  1 _ 300 A are not yet allocated to any of the applications  500 . 
     The element of “remaining resource amount  1605 ” thus shows the same value as in the element of “resource amount  1604 ” for each of the hardware resources in the partition  1 _ 300 A. The hardware resources in the partition  1 _ 300 A are not yet turned ON, and thus the element of “power source  1606 ” stores “OFF” for each of the hardware resources. Moreover, the elements of “located application  1607 ” and “application resource amount  1608 ” are both blank for each of the hardware resources in the partition  1300 A. 
     On the other hand, at the point in time before migration of the application  500 A in  FIG. 14 , the partition  2 _ 300 B includes the application  500 A. Therefore, the element of “located application  1607 ” for the partition  2 _ 300 B stores the identifier of the application  500 A, e.g., “APP1” in  FIG. 16A  example. In this state, the hardware resources in the partition  2 _ 300 B are all turned ON, and thus the element of “power supply  1606 ” stores “ON” for each of the hardware resources. 
     Assuming that, in the partition  2 _ 300 B, when the resources of “5” of the server  120  are allocated to the application  500  out of “10” being the entire resource amount, when the resources of “1” of the FC-SW  140  are allocated to the application  500  out of “10” being the entire resource amount, and when the resources of “6” of the storage device  100  are allocated to the application  500  out of “10” being the entire resource amount, the element of “application resource amount  1608 ” stores “5”, “1”, and “6” respectively for the server  120 , the FC-SW  140 , and the storage device  100  in the partition  2 _ 300 B. The element of “remaining resource amount  1605 ” thus stores “5”, “9”, and “4” therefor respectively. 
       FIG. 16B  is a diagram illustrating the application management table  136 B. The application management table  136 B includes information for management use of the applications  500  running on the computer system under the management of the management server  130 . 
     To be specific, the application management table  136 B includes elements of “application name  1621 ”, “located partition number  1622 ”, “located server name  1623 ”, “located FC-SW name  1624 ”, “located storage name  1625 ”, “server resource amount  1626 ”, “FC-SW resource amount  1627 ”, and “storage resource amount  1628 ”. 
     The element of “application name  1621 ” is information for use to identify the application  500  running in the computer system. 
     The element of “located partition number  1622 ” is information for use to identify the partition including each of the applications  500 . 
     The element of “located server name  1623 ” is information for use to identify the server  120  including the virtual server  601  of each of the applications  500 . 
     The element of “located FC-SW name  1624 ” is information for use to identify the FC-SW  140  including the logical path  602  of each of the applications  500 . 
     The element of “located storage name  1625 ” is information for use to identify the storage device  100  including the logical volume  603  of each of the applications  500 . 
     The element of “server resource amount  1626 ” indicates the amount of resources of the server  120  allocated to each of the applications  500 . 
     The element of “FC-SW resource amount  1627 ” indicates the amount of resources of the FC-SW  140  allocated to each of the applications  500 . 
     The element of “storage resource amount  1628 ” indicates the amount of resources of the storage device  100  allocated to each of the applications  500 . 
     The time frame of  FIG. 16B  example is, in  FIG. 14 , before the application  500 A is migrated from the partition  2 _ 300 B to the partition  1 _ 300 A. That is, at the point in time, the application  500 A is located in the partition  2 _ 300 B. Therefore, in  FIG. 16B  example, for the elements corresponding to “APP1” in the element of “application name  1621 ”, i.e., elements of “located partition number  1622 ”, “located server name  1623 ”, “located FC-SW name  1624 ”, and “located storage name  1625 ”, “2”, “server P 2 ”, “FC-SW P 2 ”, and “storage P 2 ” are respectively stored. These values are consistent with in  FIG. 16A  example. Moreover, as shown in  FIG. 16A , “5”, “1”, and “6” are respectively stored in the elements of “server resource amount  1626 ”, “FC-SW resource amount  1627 ”, and “storage resource amount  1628 ”. 
     Described next is a process of migrating the application  500 , and a process of power supply control in association therewith by referring to the flowchart. In the description below, as a specific exemplary process, the processes of  FIGS. 14 and 15  are referred to, i.e., the process of migrating the application  500 A, and the process of power supply control therefor. 
       FIG. 17  is an overall flowchart of the process of migrating the application  500  and the process of power supply control to be executed in the embodiment of the invention. 
     This process is executed in step  1002  of  FIG. 10 . 
     After the migration process is started for the application  500  (step  1701 ), first of all, the management program  135  of the management server  130  starts executing a storage power-ON process (step  1702 ). This is the process of turning ON the storage device  100  being a migration destination, i.e., the storage device  100  in the partition  1 _ 300 A in  FIG. 14  example. 
     The storage power-ON process to be executed in step  1702  will be described in detail later by referring to  FIG. 18 . 
     After completion of the storage power-ON process, i.e., after completion of the activation process of the storage device  100  being a migration destination, the management program  135  starts executing a full copy process of the logical volume  603  (step  1703 ). The full copy process to be executed in step  1703  will be described in detail later by referring to  FIGS. 19 and 20 . 
     After completion of the full copy process in step  1703 , the management program  135  executes a server power-ON process (step  1704 ). This is the process of turning ON the server  120  being a migration destination. The server power-ON process to be executed in step  1704  will be described in detail later by referring to  FIG. 21 . 
     After completion of the full copy process in step  1703 , the management program  135  then executes an FC-SW power-ON process (step  1705 ). This is the process of turning ON the FC-SW  140  being a migration destination. The FC-SW power-ON process to be executed in step  1705  will be described in detail later by referring to  FIG. 22 . 
     After completion of the full copy process in step  1703 , the management program  135  then executes a differential copy process of the logical volume  603  (step  1706 ). The differential copy process to be executed n step  1706  will be described in detail later by referring to  FIGS. 23 and 24 . 
     To determine whether the full copy process is completed or not, the management program  135  may use as a basis a message of completion provided by the storage device  100 , or may use as a basis a full copy processing time of its own calculation. 
     If with the former case, the end time of the full copy process is the time when the management server  130  is provided with the message of completion by the storage device  100 , and when the time comes, the processes in steps  1704  to  1706  are responsively executed. The message of completion will be described later (refer to  FIG. 20 ). 
     If with the latter case, the end time of the full copy process is after the expiration of time of the full copy process, and when the time comes, the processes in steps  1704  to  1706  are responsively executed. The full copy processing time is calculated by dividing the capacity of the logical volume  603 F being a copy source by the data transfer speed from the logical volume  603 F to the logical volume  603 A being a copy destination. The data transfer speed may be calculated based on the specifications of the hardware resources, or may be any actual measurement value. 
     Note that  FIG. 17  shows steps  1704  to  1706  in sequential order for the sake of convenience, but this order is just an example. These three steps are required to be executed in response to completion of the full copy process in step  1703 , but the execution order thereof is not restrictive. If possible, these three steps may be executed all at once. However, as described by referring to  FIG. 15 , to produce the effects of reduction of power consumption in this embodiment, steps  1704  and  1705  are required to be started before no later than the completion of the differential copy process. 
     After completion of the server power-ON process, the FC-SW power-ON process, and the differential copy process (steps  1704  to  1706 ), the management program  135  executes the migration process for the logical path  602  (step  1707 ). This process will be described in detail later by referring to  FIG. 25 . 
     After completion of the migration process for the logical path  602  in step  1707 , the management program  135  executes the migration process for the virtual server  601  (step  1708 ). This process will be described in detail later by referring to  FIG. 26 . 
     After completion of the migration process for the virtual server  601  in step  1708 , the management program  135  ends the migration process for the application  500  (step  1709 ). Note that after completion of the migration process for the virtual server  601 , e.g., in step  1709 , the hardware resources in the partition being a migration source, i.e., the server  120 , the FC-SW  140 , and the storage device  100  in the partition  2 _ 300 B in  FIG. 14  example, may be turned OFF. 
       FIG. 18  is a flowchart of the storage power-ON process to be executed in the embodiment of the invention. 
     This process is to be executed in step  1702  of  FIG. 17 . 
     When the storage power-ON process is started (step  1801 ), the management program  135  checks the hardware resources being a target (step  1802 ). To be specific, the management program  135  refers to the partition management table  136 A, and checks the state of the storage device  100  found in the partition being a migration destination, i.e., the storage device being a migration destination. 
     When the partition  1 _ 300 A is designated as a migration destination as in  FIG. 14  example, for example, the management program  135  refers to the partition management table  136 A, and specifies every entry corresponding to “1” in the element of “partition number  1601 ” and “storage  1 ” in the element of “hardware type  1602 ”. The management program  135  then checks the values in the element of “power supply  1606 ” for the specified every entry. 
     The management program  135  then determines whether or not the storage device  100  being a migration destination is in the state of power OFF, i.e., “OFF” state (step  1803 ). To be specific, the management program  135  determines whether the value acquired in step  1802  is “ON” or “OFF”. 
     When the storage device  100  being a migration destination has been already turned ON, there is no more need to execute the process of power ON, and thus the management program  135  ends the storage power-ON process (step  1806 ). 
     When the storage device  100  being a migration destination has been turned OFF, the management program  135  forwards a power-ON command to the storage device  100  being a migration destination over the management network  150  (step  1804 ). Upon reception of the power-ON command via the I/F  104 , the power supply control section  105  of the storage device  100  turns ON the storage device  100 . Note that, for execution of such a process, at least the I/F  104  and the power supply control section  105  in the storage device  100  are required to be turned ON when the storage power-ON process is started. 
     The storage device  100  is turned ON in accordance with the power-ON command, and when the activation process is through, may forward a notification to the management server  130  that the activation process is now completed. 
     The management program  135  then updates the information about the power supply in the management table  136  to reflect the result of the storage power-ON process (step  1805 ). 
     When a plurality of entries are specified in step  1802 , i.e., when the partition being a migration destination includes a plurality of storage devices  100 , each of the entries is subjected to the processes in steps  1803  to  1805 . 
     This is the end of the storage power-ON process (step  1806 ). 
     In  FIG. 16A  example, in step  1802 , specified is only the entry of  1613  including “storage P 1 ” for the element of “hardware name  1603 ”. Because the value in the element of “power supply  1606 ” for the entry  1613  is “OFF”, in step  1804 , the management program  135  forwards the power-ON command to the storage device  100  being a migration destination, i.e., the storage device  100  identified by “storage P 1 ”. This accordingly turns ON the storage device  100  in the partition  1 _ 300 A being a migration destination, and in step  1805 , the value in the element of “power supply  1606 ” for the entry  1613  is updated to “ON”. 
       FIG. 19  is a flowchart of the full copy process for the logical volume  603  to be executed by the management server  130  in the embodiment of the invention. 
     The full copy process for the logical volume  603  is a part of the migration process for the logical volume  603  as described by referring to  FIG. 15 . This process is executed in step  1703  of  FIG. 17 . 
     When the migration process is started for the logical volume  603  (step  1901 ), the management program  135  starts the full copy process for the logical volume  603  (step  1902 ), performs the full copy (step  1903 ), and ends the full copy process (step  1904 ). 
     To be specific, in step  1903 , the management program  135  forwards a full copy command to the storage device  100  being a migration source. The process to be executed by the storage device  100  provided with such a command will be described in detail later by referring to  FIG. 20 . 
       FIG. 20  is a flowchart of the full copy process for the logical volume  603  to be executed by the storage device  100  in the embodiment of the invention. 
     This process is executed by the controller  101  of the storage device  100  provided by the command forwarded in step  1903  of  FIG. 19 , i.e., the storage device  100  in the partition  2 _ 300 B in  FIG. 14  example. 
     When the full copy process is started for the logical volume  603  (step  2001 ), the controller  101  reserves the storage area for storage of a differential I/O (step  2002 ). This storage area may be reserved in the vacant storage area of any of the logical volumes  111  under the management of the storage device  100 , for example. 
     The controller  101  then changes the execution target for data I/O to/from the logical volume  603  being a migration target to the storage area reserved in step  2002  (step  2003 ). Thereafter, upon reception of the data I/O to/from the logical volume  603  being a migration target, i.e., the logical volume  603 F in  FIG. 14  example, the controller  101  stores the resulting data updated thereby in the storage area reserved in step  2002  as a differential stock without reflecting the data to the logical volume  603  (refer to  FIG. 11 ). 
     The controller  101  then performs the full copy of the logical volume  603  (step  2004 ). In  FIG. 14  example, the controller  101  reads the data of the logical volume  603 F in its entirety, and forwards a request to the storage device  100  in the partition  1 _ 300 A for writing the data being the reading result into the logical volume  603 A. Note here that the logical volume  603  being a copy source and destination is designated by an argument found in the command provided in step  1903  of  FIG. 19 . 
     After completion of the transmission of the entire data being the reading result, the controller  101  ends the full copy process for the logical volume  603  (step  2005 ). At this time, the controller  101  forwards a message of completion to the management server  130  to notify that the full copy process is now ended. 
     Upon reception of the message of completion provided in step  2005 , the management program  135  responsively executes the processes in steps  1704  to  1706 . 
     Herein, as described by referring to  FIG. 17 , the management program  135  may calculate the full copy processing time based on the specifications of the hardware resources, for example, and based on the full copy processing time being the calculation result, may controllably execute the processes in steps  1704  to  1706 . If this is the case, the controller  101  has no more need to forward the message of completion in step  2005 . 
       FIG. 21  is a flowchart of the server power-ON process to be executed in the embodiment of the invention. 
     This process is executed in step  1704  of  FIG. 17 . That is, this process is executed in response to the management server  130  receiving the message of completion provided in step  2005  of  FIG. 20 . 
     When the storage power-ON process is started (step  2101 ), the management program  135  checks the hardware resources being a target (step  2102 ). To be specific, the management program  135  refers to the partition management table  136 A, and checks the state of the server  120  found in the partition being a migration destination, i.e., the server being a migration destination. 
     When the partition  1 _ 300 A is designated as a migration destination as in  FIG. 14  example, the management program  135  refers to the partition management table  136 A, and specifies every entry corresponding to “1” in the element of “partition number  1601 ”, and “server  1 ” in the element of “hardware type  1602 ”. The management program  135  then checks the value in the element of “power supply  1606 ” for every specified entry. 
     The management program  135  then determines whether or not the server  120  being a migration destination is in the state of power OFF, i.e., “OFF” state (step  2103 ). To be specific, the management program  135  determines whether the value acquired in step  2102  is “ON” or “OFF”. 
     When the server  120  being a migration destination has been already ON, there is no more need to execute the process of power ON, and thus the management program  135  ends the server power-ON process (step  2106 ). 
     When the server  120  being a migration destination has been turned OFF, the management program  135  forwards a power-ON command to the server  120  being a migration destination over the management network  150  (step  2104 ). Upon reception of the power-ON command via the I/F  125 , the power supply control section  123  of the server  120  turns ON the server  120 . Note that, for execution of such a process, at least the I/F  125  and the power supply control section  123  in the server  120  are required to be turned ON when the server power-ON process is started. 
     The server  120  is turned ON in accordance with the power-ON command, and when the activation process is through, may forward a notification to the management server  130  that the activation process is now completed. 
     The management program  135  then updates the information about the power supply in the management table  136  to reflect the result of the server power-ON process (step  2105 ). 
     When a plurality of entries are specified in step  2102 , i.e., when the partition being a migration destination includes a plurality of servers  120 , each of the entries is subjected to the processes in steps  2103  to  2105 . 
     This is the end of the server power-ON process (step  2106 ). 
     In  FIG. 16A  example, in step  2102 , specified is only the entry of  1611  including “server P 1 ” for the element of “hardware name  1603 ”. Because the value in the element of “power supply  1606 ” for the entry  1611  is “OFF”, in step  2104 , the management program  135  forwards the power-ON command to the server  120  being a migration destination, i.e., the server  120  identified by “server P 1 ”. This accordingly turns ON the server  120  in the partition  1 _ 300 A being a migration destination, and in step  2105 , the value in the element of “power supply  1606 ” for the entry  1611  is updated to “ON”. 
     Note that, as in  FIG. 14  example, when one or more servers  120  are allocated to each of the partitions, in step  2104 , a command is transmitted for turning ON the server(s)  120  in the partition being a migration destination, i.e., a command for turning ON the entire resources in the server(s)  120 . However, as shown in  FIG. 4 , for example, when the resource portions of one server  120 , e.g., CPUs  121 , are respectively allocated to the partitions, and when the resource portions can be separately turned ON, in step  2104 , a command is forwarded to the server  120  including the resource portion for turning ON the resource portions of the server(s)  120  in the partition being a migration destination. Upon reception of the command, the power supply control section  123  of the server  120  accordingly turns ON the resource portion designated by the command, e.g., the designated CPU. 
       FIG. 22  is a flowchart of the FC-SW power-ON process to be executed in the embodiment of the invention. 
     This process is executed in step  1705  of  FIG. 17 . That is, this process is executed in response to the management server  130  receiving the message of completion provided in step  2005  of  FIG. 20 . 
     When the FC-SW power-ON process is started (step  2201 ), the management program  135  checks the hardware resources being a target (step  2202 ). To be specific, the management program  135  refers to the partition management table  136 A, and checks the state of the FC-SW  140  found in the partition being a migration destination, i.e., the FC-SW being a migration destination. 
     When the partition  1 _ 300 A is designated as a migration destination as in  FIG. 14  example, the management program  135  refers to the partition management table  136 A, and specifies every entry corresponding to “1” in the element of “partition number  1601 ”, and “FC-SW  1 ” in the element of “hardware type  1602 ”. The management program  135  then checks the value in the element of “power supply  1606 ” for every specified entry. 
     The management program  135  then determines whether or not the FC-SW  140  being a migration destination is in the state of power OFF, i.e., “OFF” state (step  2203 ). To be specific, the management program  135  determines whether the value acquired in step  2202  is “ON” or “OFF”. 
     When the FC-SW  140  being a migration destination has been already ON, there is no more need to execute the process of power ON, and thus the management program  135  ends the FC-SW power-ON process (step  2206 ). 
     When the FC-SW  140  being a migration destination has been turned OFF, the management program  135  forwards the power-ON command to the FC-SW  140  being a migration destination over the management network  150  (step  2204 ). Upon reception of the power-ON command via the I/F  142 , the power supply control section  143  of the FC-SW  140  turns ON the FC-SW  140 . Note that, for execution of such a process, at least the I/F  142  and the power supply control section  143  in the FC-SW  140  are required to be turned ON when the FC-SW power-ON process is started. 
     The FC-SW  140  is turned ON in accordance with the power-ON command, and when the activation process is through, may forward a notification to the management server  130  that the activation process is now completed. 
     The management program  135  then updates the information about the power supply in the management table  136  to reflect the result of the FC-SW power-ON process (step  2205 ). 
     When a plurality of entries are specified in step  2202 , i.e., when the partition being a migration destination includes a plurality of FC-SWs  140 , each of the entries is subjected to the processes in steps  2203  to  2205 . 
     This is the end of the FC-SW power-ON process (step  2206 ). 
     In  FIG. 16A  example, in step  2202 , specified is only the entry of  1612  including “FC-SW P 1 ” for the element of “hardware name  1603 ”. Because the value in the element of “power supply  1606 ” for the entry  1612  is “OFF”, in step  2204 , the management program  135  forwards the power-ON command to the FC-SW  140  being a migration destination, i.e., the FC-SW  140  identified by “FC-SW P 1 ”. This accordingly turns ON the FC-SW  140  in the partition  1 _ 300 A being a migration destination, and in step  2205 , the value in the element of “power supply  1606 ” for the entry  1612  is updated to “ON”. 
       FIG. 23  is a flowchart of the differential copy process for the logical volume  603  to be executed by the management server  130  in the embodiment of the invention. 
     The differential copy process for the logical volume  603  is a part of the migration process for the logical volume  603  as described by referring to  FIG. 15 . This process is executed in step  1706  of  FIG. 17 . 
     When the differential copy process is started for the logical volume  603  (step  2301 ), the management program  135  starts the differential copy process (step  2302 ). To be specific, the management program  135  forwards a differential copy command to the storage device  100  being a migration source. The process to be executed by the storage device  100  provided such a command will be described in detail later by referring to  FIG. 24 . 
     The management program  135  then updates the management table  136  to reflect the result of copying executed as above (step  2303 ). When the copy process is executed from the logical volume  603 F to  603 A as shown in  FIG. 14 , in the partition management table  136 A, the entries  1613  and  1616  related to the storage device  100  are updated. 
     In  FIG. 16A  example, the storage device  100  including the logical volume  603 A corresponds to the entry  1613 , and the storage device  100  including the logical volume  603 F corresponds to the entry  1616 . In this case, the element of “resource amount  1604 ” shows “6” for the logical volume  603 F before the copy process. As a result of the copy process from the logical volume  603 F to  603 A, the logical volume  603 F being a part of the application  500 A does not use the resources any more, but the logical volume  603 A instead starts using the resources as a part of the application  500 A. 
     As such, in step  2303 , the elements for the entry  1613 , i.e., the elements of “remaining resource amount  1605 ”, “located application  1607 ”, and “application resource amount  1608 ”, are updated to “4”, “APP1”, and “6”, respectively. On the other hand, the element of “remaining resource amount  1605 ” for the entry  1616  is updated to “10”, and the elements of “located application  1607 ” and “application resource amount  1608 ” for the entry  1616  are both updated to blank. 
     Then in step  2303 , the application management table  136 B is also updated. To be specific, the element of “located storage name  1625 ” for the “APP1” in the element of “application name  1621 ” is updated to “storage P 1 ”. 
     After execution of the process in step  2303 , the management program  135  ends the differential copy process for the logical volume  603  (step  2304 ). As such, the migration process is ended for the logical volume  603  (step  2305 ). 
       FIG. 24  is a flowchart of the differential copy process for the logical volume  603  to be executed by the storage device  100  in the embodiment of the invention. 
     This process is executed by the controller  101  of the storage device  100  provided with the command transmitted in step  2302  of  FIG. 23 , i.e., the storage device  100  in the partition  2 _ 300 B in  FIG. 14  example. 
     After the differential copy process is started for the logical volume  603  (step  2401 ), the controller  101  stops data I/O to/from the logical volume  603  being a copy source, i.e., the logical volume  603 F in  FIG. 14  example (step  2402 ). Herein, because the execution destination for the data I/O has been already changed in step  2003  of  FIG. 20 , in step  2402 , the data I/O to/from the storage area of the differential data I/O is stopped. 
     The controller  101  then performs the differential copy (step  2403 ). To be specific, the controller  101  forwards a request, to the storage device  100  in the partition  1 _ 300 A, for data reading from the storage area of the differential data I/O, and for writing the data being the reading result to the logical volume  603 A being a copy destination. 
     After completion of transmission of the differential data in its entirety, the controller  101  deletes the reserved storage area of the differential data I/O (step  2404 ). 
     As such, the controller  101  ends the differential copy process for the logical volume  603  (step  2405 ). 
     Note here that the data I/O stopped in step  2402  is resumed by a migration process for the logical path  602  that will be described later (refer to  FIG. 25 ). 
       FIG. 25  is a flowchart of the migration process for the logical path  602  to be executed in the embodiment of the invention. 
     This process is executed in step  1707  of  FIG. 17 . 
     After the migration process is started for the logical path  602  (step  2501 ), the management program  135  migrates the logical path  602  (step  2502 ). For migration of the logical path  602 A as shown in  FIG. 14 , for example, the management program  135  may forward a command to the server  120  in the partition  2 _ 300 B for migrating the logical path  602 A. Upon reception of this command, the server  120  may change the settings of the path management program  127  to allow the logical path  602 A to be connected to the logical volume  603 A via the FC-SW  140  in the partition  1 _ 300 A. 
     After migration of the logical path  602 A in step  2502 , the storage device  100  in the partition  1 _ 300 A resumes data I/O to/from the logical volume  603 A. 
     The management program  135  then updates the management table  136  to reflect the migration of the logical path  602  in step  2502  (step  2503 ). When the logical path  602 A is migrated as shown in  FIG. 14 , for example, in the partition management table  136 A, the entries of  1612  and  1615  related to the FC-SW  140  are updated. 
     In  FIG. 16A  example, the FC-SW  140  in the partition  1 _ 300 A corresponds to the entry  1612 , and the FC-SW  140  in the partition  2 _ 300 B corresponds to the entry  1615 . In this case, the FC-SW  140  in the partition  2 _ 300 B used by the logical path  602 A before the migration shows the resource amount of “1”. As a result of the migration in step  2502 , the logical path  602 A does not use the resources of the FC-SW  140  in the partition  2 _ 300 B anymore, but instead starts using the resources of the FC-SW  140  in the partition  1 _ 300 A. 
     As such, in step  2503 , the elements for the entry  1612 , i.e., the elements of “remaining resource amount  1605 ”, “located application  1607 ”, and “application resource amount  1608 ”, are updated to “9”, “APP1”, and “1”, respectively. On the other hand, the element of “remaining resource amount  1605 ” for the entry  1615  is updated to “10”, and the elements of “located application  1607 ” and “application resource amount  1608 ” for the entry  1615  are both updated to blank. 
     Then in step  2503 , the application management table  136 B is also updated. To be specific, the element of “located FC-SW name  1624 ” for the “APP1” in the element of “application name  1621 ” is updated to “FC-SW P 1 ”. 
     As such, the migration process is ended for the logical path  602  (step  2504 ). 
       FIG. 26  is a flowchart of a migration process for the virtual server  601  to be executed in the embodiment of the invention. 
     This process is executed in step  1708  of  FIG. 17 . 
     When the migration process is started for the virtual server  601  (step  2601 ), the management program  135  migrates the virtual server  601  (step  2602 ). As described by referring to  FIG. 9 , for example, this migration is performed by copying an image of the memory  122 . 
     The management program  135  then updates the management table  136  to reflect the migration of the virtual server  601  in step  2602  (step  2603 ). When the virtual server  601 A is migrated as shown in  FIG. 14 , for example, in the partition management table  136 A, the entries of  1611  and  1614  related to the server  120  are updated. 
     In  FIG. 16A  example, the server  120  in the partition  1 _ 300 A corresponds to the entry  1611 , and the server  120  in the partition  2 _ 300 B corresponds to the entry  1614 . In this case, the server  120  in the partition  2 _ 300 B used by the virtual server  601 A before the migration shows the resource amount of “1”. As a result of the migration in step  2602 , the virtual server  601 A does not use the resources of the server  120  in the partition  2 _ 300 B anymore, but instead starts using the resources of the server  120  in the partition  1 _ 300 A. 
     As such, in step  2603 , the elements for the entry  1611 , i.e., the elements of “remaining resource amount  1605 ”, “located application  1607 ”, and “application resource amount  1608 ”, are updated to “5”, “APP1”, and “5”, respectively. On the other hand, the element of “remaining resource amount  1605 ” for the entry  1614  is updated to “10”, and the elements of “located application  1607 ” and “application resource amount  1608 ” for the entry  1614  are both updated to blank. 
     Then in step  2603 , the application management table  136 B is also updated. To be specific, the element of “located server name  1623 ” for the “APP1” in the element of “application name  1621 ” is updated to “server P 1 ”. 
     As such, the migration process is ended for the virtual server  601  (step  2604 ). 
       FIG. 27  is a flowchart of a migration-destination partition state check process to be executed in the embodiment of the invention. 
     This process is executed in step  804  of  FIG. 8 . 
     When the migration-destination partition state check process is started (step  2701 ), the management program  135  checks the partition currently including the application  500  being a migration target (step  2702 ). For check as such, the application management table  136 B is referred to, i.e., the elements of “located partition number  1622 ” to “located storage name  1625 ”. 
     The management program  135  then selects the resources being a migration destination, i.e., the partition being a migration destination (step  2703 ). 
     The management program  135  then refers to the partition management table  136 A, and checks the state of the storage device  100  found in the partition selected as a migration destination (hereinafter, referred to as selected storage device) (step  2704 ). 
     Based on the check result in step  2704 , the management program  135  determines whether or not the application  500  is allowed for migration to the selected storage device  100 , i.e., allowed for copy of the data in the logical volume  603  (step  2705 ). 
     When the determination result tells that the application  500  is allowed for migration to the selected storage device  100 , the management program  135  refers to the partition management table  136 A, and checks the state of the FC-SW  140  found in the partition selected as a migration destination (hereinafter, referred to as selected FC-SW) (step  2706 ). 
     Based on the check result in step  2706 , the management program  135  then determines whether or not the application  500  is allowed for migration to the selected FC-SW  140 , i.e., for migration of the logical path  602  (step  2707 ). 
     When the determination result tells that the application  500  is allowed for migration to the selected FC-SW  140 , the management program  135  refers to the partition management table  136 A, and checks the state of the server  120  found in the partition selected as a migration destination (hereinafter, referred to as selected server) (step  2708 ). 
     Based on the check result in step  2708 , the management program  135  then determines whether or not the application  500  is allowed for migration to the selected server  120 , i.e., for migration of the virtual server  601  (step  2709 ). 
     In step  2709 , when the determination result tells that the application  500  is allowed for migration to the selected server  120 , it means that the application  500  can be migrated to the partition selected as a migration destination. The management program  135  thus ends the process after forwarding a response to notify that the application is allowed for migration (step  2710 ). In this case, in step  805  of  FIG. 8 , the determination is so made that the application  500  is allowed for migration to the selected partition. 
     On the other hand, when the application  500  is determined as not being allowed for migration at least one of steps  2705 ,  2707 , or  2709 , it means that the application  500  cannot be migrated to the partition selected as a migration destination. The management program  135  thus ends the process after forwarding a response to notify that the application is not allowed for migration (step  2711 ). In this case, in step  805  of  FIG. 8 , the determination is so made that the application  500  is not allowed for migration to the selected partition. 
     Described now is a specific example of the process of  FIG. 27  by taking as an example the migration of the application  500 A of  FIG. 14 . 
     The management table  136  before the migration of the application  500 A of  FIG. 14  is as shown in  FIG. 16 . In this case, in step  2702 , the values in the elements confirm that the application  500 A is located in the partition  2 _ 300 B, i.e., “2” in the element of “located partition number  1622 ”, “server P 2 ” in the element of “located server name  1623 ”, “FC-SW P 2 ” in the element of “located FC-SW name  1624 ”, and “storage P 2 ” in the element of “located storage name  1625 ”. 
     Then in step  2703 , the element of “partition number  1601 ” is referred to, and the partition other than the partition  2 _ 300 B currently including the application  500 A is selected as a migration destination, i.e., the partition  1 _ 300 A. 
     In step  2704 , the element of “remaining resource amount  1605 ” is referred to for the entry corresponding to the storage device  100  found in the partition  1 _ 300 A, i.e., the entry  1613  in  FIG. 16A  example. 
     In step  2705 , a value comparison is made between in the element of “remaining resource amount  1605 ” referred to in step  2704  and in the element of “storage resource amount  1628 ”. When the value in the element of “remaining resource amount  1605 ” is smaller than the value in the element of “storage resource amount  1628 ”, migrating the application  500 A will cause a shortage of the resources of the partition  1 _ 300 A being a migration destination, e.g., the capacity of the storage device  100 , whereby the application  500 A cannot be migrated. In  FIG. 16A  example, the value of “10” in the element of “remaining resource amount  1605 ” is larger than the value of “6” in the element of “storage resource amount  1628 ” so that the application  500 A is determined as being possible for migration. 
     In step  2706 , the element of “remaining resource amount  1605 ” is referred to for the entry corresponding to the FC-SW  140  found in the partition  1 _ 300 A, i.e., the entry  1612  in  FIG. 16A  example. 
     In step  2707 , a value comparison is made between in the element of “remaining resource amount  1605 ” referred to in step  2706  and in the element of “FC-SW resource amount  1627 ”. When the value in the element of “remaining resource amount  1605 ” is smaller than the value in the element of “FC-SW resource amount  1627 ”, migrating the application  500 A will cause a shortage of the resources of the partition  1 _ 300 A being a migration destination, e.g., the port  141  of the FC-SW  140 , whereby the application  500 A cannot be migrated. In  FIG. 16A  example, the value of “10” in the element of “remaining resource amount  1605 ” is larger than the value of “1” in the element of “FC-SW resource amount  1627 ” so that the application  500 A is determined as being possible for migration. 
     In step  2708 , the element of “remaining resource amount  1605 ” is referred to for the entry corresponding to the server  120  found in the partition  1 _ 300 A, i.e., the entry  1611  in  FIG. 16A  example. 
     In step  2709 , a value comparison is made between in the element of “remaining resource amount  1605 ” referred to in step  2708  and in the element of “server resource amount  1626 ”. When the value in the element of “remaining resource amount  1605 ” is smaller than the value in the element of “server resource amount  1626 ”, migrating the application  500 A will cause a shortage of the resources of the partition  1 _ 300 A being a migration destination, e.g., the CPU  121  of the server  120 , whereby the application  500 A cannot be migrated. In  FIG. 16A  example, the value of “10” in the element of “remaining resource amount  1605 ” is larger than the value of “5” in the element of “server resource amount  1626 ” so that the application  500 A is determined as being possible for migration. 
       FIGS. 28A and 28B  are each a diagram illustrating the management table  136  after migration of the application  500  in the embodiment of the invention. 
     To be specific,  FIG. 28A  shows the partition management table  136 A of  FIG. 16A , and  FIG. 28B  shows the application management table  136 B of  FIG. 16B . The partition management table  136 A and the application management table  136 B are both being the update results by the processes of  FIGS. 17 to 26 . That is,  FIGS. 28A and 28B  respectively show the partition management table  136 A and the application management table  136 B after the application  500 A is migrated as shown in  FIG. 14 . 
     The application  500 A identified by the application name of “APP1” is now migrated to the partition  1 _ 300 A. Therefore, in the application management table  136 B, the elements corresponding to the application name of “APP1”, i.e., the elements of “located partition number  1622 ”, “located server name  1623 ”, “located FC-SW name  1624 ”, and “located storage name  1625 ”, are updated to “1”, “server P 1 ”, “FC-SW P 1 ”, and “storage P 1 ”, respectively. 
     Then in the partition management table  136 A, the element of “power supply  1606 ” is entirely updated to “ON” for the entries  1611  to  1613  corresponding to the partition  1 _ 300 A, and the element of “located application  1607 ” is entirely updated to “APP1” therefor. Moreover, the elements of “remaining resource amount  1605 ” and “application resource amount  1608 ” corresponding to the “server P 1 ” are respectively updated to “5” and “5”, the elements of “remaining resource amount  1605 ” and “application resource amount  1608 ” corresponding to the “FC-SW P 1 ” are respectively updated to “9” and “1”, and the elements of “remaining resource amount  1605 ” and “application resource amount  1608 ” corresponding to the “storage P 1 ” are respectively updated to “4” and “6”. 
     On the other hand, the element of “remaining resource amount  1605 ” for the entries  1614  to  1616  corresponding to the partition  2 _ 300 B is entirely updated to “10” to be the same as in the element of “resource amount  1604 ”. The element of “power supply  1606 ” is entirely updated to “OFF”, and the elements of “located application  1607 ” and “application resource amount  1608 ” are entirely updated to blank. 
       FIG. 29  is a diagram illustrating a modified example of the migration process for the application  500  and the power supply control process to be executed in the embodiment of the invention. 
     In the process of  FIG. 17  described above, the server power-ON process (step  1704 ) and the FC-SW power-ON process (step  1705 ) are both started in response to completion of the full copy process of the logical volume  603 . On the other hand, in  FIG. 29 , the start time is calculated for both the server power-ON process and the FC-SW power-ON process. 
     As described by referring to  FIG. 15 , it is desirable to start the server power-ON process and the FC-SW power-ON process in such a manner that the various processes are to be completed at the same time, i.e., the differential copy process, the activation process for the server  120 , and the activation process for the FC-SW  140 , that is, in such a manner that the tips of the arrows  1503 ,  1504 , and  1505  come at the same time. However, correctly estimating the time needed for the differential copy process is difficult, and thus in the process of  FIG. 17 , the end time for the full copy process is used as the time optimally approximate to start the server power-ON process and the FC-SW power-ON process. 
     On the other hand, in the process of  FIG. 29 , by approximately calculating the time needed for the differential copy process, the time is set for starting the server power-ON process and the FC-SW power-ON process. 
     Described now is the process of  FIG. 29 . The process of  FIG. 29  is executed as an alternative to the process of  FIG. 17 , i.e., executed in step  1002  of  FIG. 10 . 
     When the migration process is started for the application  500  (step  2901 ), first of all, the management program  135  of the management server  130  executes the storage power-ON process (step  2902 ). These processes are similarly executed to the processes in steps  1701  and  1702  of  FIG. 17 , respectively, and thus are not described twice. 
     After completion of the storage power-ON process, the management program  135  executes the full copy process of the logical volume  603  (step  2903 ). This process is similar to the process in step  1703  of  FIG. 17 . 
     After completion of the full copy process of the logical volume  603 , the management program  135  executes the differential copy process of the logical volume  603  (step  2904 ). This process is similar to the process in step  1706  of  FIG. 17 . 
     The management program  135  goes through steps  2905  to  2909  at the same time as steps  2903  and  2904 . 
     To be specific, after the full copy process is started for the logical volume  603 , calculated is a time when the differential copy process will be ended for the logical volume  603 , i.e., estimated end time (step  2905 ). This process is started in response to completion of copying of a predetermined proportion of data to be copied by the full copy process, e.g., 80%, 90%, or 100%. Exemplified here is a case where the predetermined proportion is 90% in step  2905 . Note here that the process in step  2905  may be executed for a plurality of times in one full copy process, e.g., at the time of completion of 80%, and at the time of completion of 90%. 
     The management program  135  estimates the amount of differential data at the time of completion of the full copy process, i.e., done with 100%. This estimation is made using the amount of data stored as a differential stock (hereinafter, referred to as differential data) when 90% of the copying is completed for the data to be copied by the full copy process. When an estimation is made that the differential I/O is generated at regular time intervals, the amount of differential data at the time when 90% of the full copy process is completed is divided by 0.9, i.e., multiplied by reciprocal of 0.9, thereby being able to calculate the amount of differential data at the time of completion of the full copy process. Although the interval of the differential I/O is generally not constant, the value being a result of calculation as above may be used as an approximate estimation value. 
     The management program  135  then calculates the time needed for copying of the differential data from the estimated value of the amount of differential data, and the transfer speed of the data transfer path for copy use. At the time of calculation as such, as the transfer speed of the data transfer path, the value being a result of actual measurement during the previous full copy process may be used. 
     The time calculated as such is added to the end time for the full copy process so that the estimated end time can be calculated for the differential copy process. 
     Herein, as described above, the end time of the full copy process for the logical volume  603  can be calculated based on the data amount of the logical volume  603 , and the transfer speed of the data transfer path. 
     Based on the estimated end time for the differential copy process calculated as such, the management program  135  then sets the time for starting the server power-ON process and the time for starting the FC-SW power-ON process (steps  2906  and  2907 ). 
     To be specific, the management program  135  calculates the time for starting the server power-ON process by subtracting the value of time needed for the activation process of the server  120  from the estimated end time for the differential copy process. When the time comes, the server power-ON process is responsively started (step  2908 ). This process is similar to the process in step  1704  of  FIG. 17 . 
     The management program  135  then calculates the time for starting the FC-SW power-ON process by subtracting the value of time needed for the activation process of the FC-SW  140  from the estimated end time for the differential copy process. When the time comes, the FC-SW power-ON process is responsively started (step  2909 ). This process is similar to the process in step  1705  of  FIG. 17 . 
     Note here that the management program  135  stores in advance information about the time needed for the activation process of the server  120  and the time needed for the activation process of the FC-SW  140 . Such time may be calculated from the specifications of the hardware resources of each of the devices, or may be values being the results of actual measurement. 
     After completion of steps  2904 ,  2908 , and  2909 , the management program executes the migration process for the logical path  602  (step  2901 ), and the migration process for the virtual server  601  (step  2911 ), thereby ending the migration process for the application  500  (step  2912 ). These steps are similar to steps  1707 ,  1708 , and  1709  of  FIG. 17 . 
     Such estimation for the end time for the differential copy process can be made with better accuracy with the smaller degree of deviation of the differential I/O, and the smaller degree of variation of the transfer speed. If with such smaller degree of deviation and variation, the power consumption in the computer system can be reduced with good efficiency. 
     Note that, as described above, the process of  FIG. 29  is executed as an alternative to the process of  FIG. 17 . The processes of  FIGS. 17 and 29  are those for turning ON the server  120  and the FC-SW  140  at any approximately optimal time for reduction of power consumption in the computer system. In either process, the time approximately optimal for turning ON the server  120  and the FC-SW  140  is calculated based on the time needed for the full copy process and for the differential copy process. As such, the technical sense of the process of  FIG. 17  is the same as that of the process of  FIG. 29 . 
       FIGS. 30A and 30B  are each a diagram illustrating the relationship between the size of the computer system and the effects thereby in the embodiment of the invention. 
       FIG. 30A  shows the application migration and the timing for power supply control in a computer system of a relatively small size, e.g., as shown in  FIG. 3  or  4 , the computer system including one to a few hardware resources in one physical partition, i.e., the server  120 , the FC-SW  140 , and the storage device  100 . The details of  FIG. 30A  are the same as those of  FIG. 15 , and thus are not described twice. 
       FIG. 30B  shows the application migration and the timing for power supply control in a computer system of a relatively large size, e.g., the computer system including several tens to several hundreds of hardware resources in one physical partition, i.e., the server  120 , the FC-SW  140 , and the storage device  100 . Such a physical partition is used as a data center, for example. The details of  FIG. 30B  are also basically the same as those of  FIG. 15 , but generally, the larger the size of the computer system, the longer time will take to activate the devices and migrate the applications. 
     For example, the time needed for migration of the logical volume  603  is dependent on the amount of transferring data as described above, but generally the time is often about a few hours in a small-size system. On the other hand, with a large-size system such as data center, migrating the logical volume  603  may sometimes take a few weeks or longer. 
     In this embodiment, as described by referring to  FIG. 15 , the power-ON time for the server  120  and that for the FC-SW  140  are made later than the start time for migration of the logical volume  603  so that the end time for migration of the logical volume  603  is controlled to be almost the same as the end time for the activation process of the server  120  and that of the FC-SW  140 . That is, the server  120  and the FC-SW  140  are not turned ON most of the time during the migration of the logical volume  603 , e.g., time during the full copy process. As such, the effects of the embodiment are enhanced if the embodiment is applied to a large-size computer system requiring a long time to migrate the logical volume  603 . 
       FIG. 31  is a diagram illustrating a fourth example of the physical partition in the embodiment of the invention. 
     A physical partition of  FIG. 31  is of a large size for use as a data center, for example. In  FIG. 31  example, the partitions  1 _ 300 A and  2 _ 300 B respectively include 20 servers, nine FC-SWs  140 , and three storage devices  100 . Note here that these numbers are each just an example, and may be much larger in a larger-sized data center. 
     In such a computer system, for migrating the data center, the need may arise for migration of applications located in the partitions. For example, for migrating a logical volume group in an application being a migration target, i.e., a group of the logical volumes  603 ,  3101 A to a logical volume group  3101 F in the partition being a migration destination, it may take a few weeks or longer as described by referring to  FIGS. 30A and 30B . By applying the embodiment to such a computer system, the server  120  and the FC-SW  140  can be favorably reduced in power consumption. 
     If the power ON time for the server  120  and that for the FC-SW  140  can be each delayed by a day through application of the embodiment, the server  120  and the FC-SW  140  can be reduced in power consumption of the day. As such, with the servers  120  being large in number and the FC-SWs  140  being large in number, the effects can be enhanced to a further degree. 
       FIG. 32  is a diagram illustrating a fifth example of the physical partition in the embodiment of the invention. 
       FIG. 32  shows an exemplary hierarchically-organized data center by partitions. In this example, the partition  1 _ 300 A is higher in hierarchy, and the partition  2 _ 300 B is lower in hierarchy. That is, the partition  1 _ 300 A has the higher processing capabilities than those of the partition  2 _ 300 B. For example, the partition  1 _ 300 A may be allocated with hardware resources of higher capabilities than those allocated to the partition  2 _ 300 B. 
     When an application group for use in a specific project is required to be executed in a partition higher in hierarchy, i.e., partition of higher performance capabilities, only for a specific time period, the copy process can be started in advance for the logical volume  603  in the application group so as to complete the migration of the application group by the time before the period. 
     In  FIG. 32  example, the partition  2 _ 300 B corresponding to a lower hierarchy (Tier 2) includes an application group  3201 A for use in a project A, and a application group  3201 B for use in a project (or business application) B. If this is the case, in this embodiment, any migration to the partition  1 _ 300 A being a higher hierarchy (Tier 1) can be controlled if needed on an application group basis. This accordingly enables to implement migration of the application groups at any desired time while reducing the power consumption in the computer system.