Abstract:
A storage device including a control part which performs control by extracting a life tag specifying a retention term during which the data is to be retained in the second volume having the quicker access time than the first volume, the control part managing the retention term of the corresponding data as specified by the life tag, and an elapsed term which has elapsed since the corresponding data was stored. A storage part manages update segment control information, and when the elapsed term of certain data exceeds the retention term of the certain data, the storage part nullifies the certain data in the second volume.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. application Ser. No. 11/034,820, filed Jan. 14, 2005 (now U.S. Pat. No. 7,380,064). This application relates to and claims priority from Japanese Patent Application No. 2004-328806, filed on Nov. 12, 2004. The entirety of the contents and subject matter of all of the above is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a storage device and a storage device data life cycle control method. 
     2. Description of the Related Art 
     In storage devices, for example, storage regions based on an RAID (redundant array of independent disks) are constructed using storage devices such as hard disk drives, semiconductor memory drives or the like. For example, such physical storage regions (logical volumes) are provided to host computers (hereafter referred to as “hosts”) such as server machines or the like. Application programs operating in the hosts provide information processing services to client terminals connected to the hosts by writing data into the logical volumes or reading out data from the logical volumes. 
     The quantities of data that must be stored by storage systems are continually increasing; furthermore, depending on the type of data, there are also cases in which long-term storage is required. Accordingly, in order to meet this increasing demand, replacement with large-capacity disk drives, or the introduction of new type high-performance storage devices, has been seen. 
     Furthermore, a technique which is devised so that virtual volumes can be constructed by virtualizing logical volumes respectively possessed by respective storage devices, and these virtual volumes can be provided to respective hosts, is also known (Japanese Patent Application Laid-Open No. 2002-91706). 
     In conventional storage systems, new types of disk drives and new types of storage devices are introduced as necessary in order to increase the storage capacity and improve the response characteristics. However, the utilization value (utilization frequency) of data is not fixed, but drops as time passes according to the type of application program and the like. For example, in the case of a data base, data groups that constitute a monthly tabulation for a certain month are frequently utilized only during the period for which the monthly tabulation is created; after this monthly tabulation is completed, these data groups are hardly used at all until the deadline for the creation of a yearly tabulation arrives, and are merely stored “as is”. Furthermore, for example, in the case of email serving program, reference is made to email data only within a relatively short period following the receipt of this email; after a reply to the email is completed, the data is stored for a long period of time without being used. 
     Accordingly, even in cases where a high-speed volume constructed by a disk drive with good response characteristics is introduced, this high-speed volume becomes filled with data groups whose utilization rate has dropped as operation is continued. Meanwhile, in cases where data stored in a low-speed volume is referred to or updated, time is required for the reading and writing of such data, so that the response characteristics drop. 
     In cases where all of the volumes are constructed by high-speed volumes, the cost is increased; accordingly, it is necessary to operate using a mixture of high-speed volumes and low-speed volumes. However, as was described above, since high-speed volumes also eventually become filled with unnecessary non-urgent data, the high-speed characteristics cannot be utilized over a long period of time. 
     Meanwhile, a technique called data migration is also known. In the case of this data migration, for example, unnecessary non-urgent data is moved from the main volume to another volume, so that the empty capacity of the main volume is maintained. In this case, for example, since the question of which data corresponds to which file, the question of which files have a low frequency of use and the like cannot be grasped on the side of the storage device, data migration is performed on the basis of instructions from the side of the host. 
     Accordingly, it is necessary to grasp the frequency of use of the respective files on the side of the host, and to move these files from the current volume to another volume, so that the operating burden on the host side is increased, and the convenience of the system is poor. For example, the user must specify the file that is the object of movement, and must give instructions for the movement of this data. Furthermore, for example, the host must read out the file that is the object of movement from the current volume, and write this read-out file into another volume, so that the burden of data input-output on the network is increased. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the present invention is to provide a storage device and a storage device data life cycle control method which are devised so that the data storage positions can be controlled in accordingly with the frequency of utilization in an environment different types of volumes are mixed. Another object of the present invention is to provide a storage device and storage device data life cycle control method which are devised so that data can be disposed while utilizing the response characteristics of a high-speed volume. Another object of the present invention is to provide a storage device and storage device data life cycle control method which make it possible to use storage resources in an efficient manner while maintaining the high-speed response characteristics of high-speed volumes in an environment in which high-speed volumes and low-speed volumes are mixed. Still other objects of the present invention will become clear from the following description of embodiments. 
     The storage device of the present invention that is used to solve the abovementioned problems comprises a first volume which stores data utilized by a host device, a second volume which stores a portion of the data contained in the data stored in the first volume, a first control part which is used to control the data stored in the second volume, a second control part which controls the correspondence relationship between the data stored in the second volume and the data stored in the first volume, a third control part which performs control by associating a storage period with the updated data when data updating is performed for the second volume, a data erasing part which detects data for which the storage period has elapsed among the data stored in the second volume, and erases this data from the second volume, and an access processing part which processes access requests from the host device by using the first control part and/or the second control part. 
     All of the data utilized by the host device can be stored in the first volume, and a portion of the data stored in the first volume can be stored in the second volume. However, at certain points in time, there may also be cases in which there is data that is stored only in the second volume, and that is not stored in the first volume. The data that is stored in the second volume is also stored in the first volume at a specified timing. Accordingly, the data that is stored in the first volume, or a portion of the data that is stored in the first volume, is stored in the second volume. 
     The first volume may also be constructed as a relatively low-speed volume, and the second volume may also be constructed as a relatively high-speed volume. In other words, all of the data that is utilized by the host device is stored in the low-speed first volume, and a portion of this data is also stored in the high-speed second volume. 
     In cases where the data that is the object of an access request from the host device is stored in both the first volume and second volume, the access processing part can process this access request using the second volume. As a result, in cases where the second volume is a high-speed volume, the response to the host device can be improved. 
     A virtual volume which is virtualized including the first volume and second volume is provide to the host device, and this virtual volume has the same storage capacity as the first volume; accordingly, the host device can send access requests to the virtual volume. 
     The virtual volume is a volume that is virtualized including the first volume and second volume, and has the same size storage space as the first volume. Specifically, the virtual volume is constructed with the data stored in the first volume and the data stored in the second volume melded together, and the host device can read and write data from and into this virtual volume. The data that is written into the virtual volume by the host device is stored in the first volume, and is also stored in the second volume for the storage period that is set for this data. 
     In cases where data is written into the virtual volume by the host device, the access processing part can write the data into the first volume in the same storage position as the storage position in the virtual volume, and can write the data into the second volume in a different storage position from the storage position in the virtual volume. 
     Specifically, the first volume and the virtual volume have the same storage space, and data that is written with the virtual volume as the object is stored in the first volume in the same storage position as the storage position in the virtual volume. On the other hand, the storage space need not coincide between the virtual volume and the second volume, and the respective data storage positions may differ between the virtual volume and the second volume. As a result, relatively new data only can be held in the second volume by using the second volume which has a smaller storage capacity than the virtual volume. 
     When data is updated for the second volume, the third control part can perform control so that a storage period is associated with this updated data. Here, for example, the storage period can be set in stages, such as 12 hours, 1 day, 3 days, 1 week, 1 month, 6 months, 1 year or the like. 
     The storage period can be set beforehand in LU (logical unit) units. Specifically, for example, the storage period can be set in advance for each virtual volume, or for each logical volume constructing the respective virtual volumes, and storage periods can be set uniformly for the data written into the volumes. Thus, the respective data storage periods can all be controlled on the side of the storage device without operating by the host device. 
     On the other hand, the storage period can also be set for specified units by the host device. In this case, the third control part controls the storage period designated by the host device. Furthermore, the host device can set the storage position in file units or directory units, or in both types of units. For example, the host device sets the storage period for specified units by issuing a write command including the storage period, and the third control part performs control by associating the storage period contained in this write command with the data that is written by this write command. Thus, the work can also be divided between the host device and the storage device by performing the setting of the storage period on the side of the host device and performing the movement of the data in accordance with the storage period on the side of the storage device. 
     The data erasing part can confirm that data that is the object of erasing is stored in the first volume, and in cases where data that is the object of erasing is not stored in the first volume, the data erasing part can delete this data that is the object of erasing from the second volume after storing this data that is the object of erasing in the first volume. Specifically, in order to ensure that data that is stored only in the second volume is not erroneously erased from the second volume, the data erasing part confirms that the data that is the object of erasing is stored in the first volume, and in cases where this data is not stored in the first volume, the data erasing part erases the data that is the object of erasing from the second volume after copying this data into the first volume. 
     In cases where a cache memory that temporarily stores the data that is written in from the host device is further provided, the access processing part stores data from the host device in the second volume if a specified empty capacity is not present in the cache memory. 
     The first volume or second volume, or both of these volumes, can be associated with the external volume of another storage device disposed on the outside, and write data aimed at the first volume or second volume can be stored in this external volume. Specifically, the external volume of another external storage device can be used as though this were an internal volume governed by the system itself. In cases where both the first volume and second volume are constructed by external volumes, it is sufficient of the storage device has only a function that controls access to the volumes and the like. Accordingly, in this case, the storage device need not be constructed as a storage device; for example, this storage device may also be constructed as a highly functionalized switch. 
     A plurality of first volumes can be provided, and a single second volume can be respectively associated with this plurality of first volumes. In other words, for example, only relatively new data (among the data respectively written into the plurality of first volumes) can be held by a single second volume. Furthermore, a construction in which second volumes are independently associated with each first volume can also be used. 
     For example, there are cases in which all or some of the functions, means and steps of the present invention are constructed as computer programs that are executed by a microcomputer. Furthermore, for example, such computer programs can be fixed and distributed in storage media such as hard disks, optical disks, semiconductor memories or the like. Moreover, such computer programs can be distributed via communications networks such as the internet or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory diagram which shows a schematic outline of an embodiment of the present invention; 
         FIG. 2  is an overall structural diagram of the storage system of a first embodiment of the present invention; 
         FIG. 3  is an explanatory diagram which shows the storage structure of the storage device; 
         FIG. 4  is a structural explanatory diagram showing the construction of the first embodiment in model form; 
         FIG. 5  is an explanatory diagram showing the construction of the mapping table; 
         FIG. 6  is an explanatory diagram respectively showing the life tag setting table and the life tag definition table; 
         FIG. 7  is an explanatory diagram showing the construction of the updating bit map table; 
         FIG. 8  is an explanatory diagram showing the construction of the updating segment control table and how data whose storage period has elapsed is erased using the updating segment control table; 
         FIG. 9  is a flow chart showing the updating processing; 
         FIG. 10  is a flow chart showing the destage processing; 
         FIG. 11  is a flow chart showing the reference processing; 
         FIG. 12  is a flow chart shown the cleaning processing; 
         FIG. 13  is a structural explanatory diagram showing the construction of a second embodiment; 
         FIG. 14  is a model diagram showing the conditions of information that is exchanged between the host and storage device during write access; 
         FIG. 15  is an explanatory diagram showing a case in which a life tag is set for each file or directory; 
         FIG. 16  is an explanatory diagram showing the program construction of the host in a case where a life tag is set by the host; 
         FIG. 17  is an explanatory diagram showing the construction of the write command; 
         FIG. 18  is a flow chart showing destage processing; 
         FIG. 19  is an explanatory diagram showing the life tag setting table used in a third embodiment; 
         FIG. 20  is an explanatory diagram showing the schematic construction of a fourth embodiment; 
         FIG. 21  is an explanatory diagram showing the LUN-FC correspondence table, with  FIG. 21  ( a ) showing a case in which respective FC volumes respectively correspond to respective LUNs, and  FIG. 21  ( b ) showing a case in which a plurality of FCs are respectively associated with a plurality of LUNs; and 
         FIG. 22  is an explanatory diagram showing the schematic construction of a fifth embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the attached figures.  FIG. 1  is an overall schematic diagram of the present embodiment. Details will be described later; however, as is shown in  FIG. 1 , the storage device  1  of the present embodiment is connected to a host  2  via a communications network such as (for example) an FC_SAN (fiber channel_storage area network) or the like. The application program (hereafter abbreviate to “application”)  2 A of the host  2  provides a specified information processing service to client terminals (not shown in the figures) by writing data into or reading data from the storage device  1 . 
     The storage device  1  comprises a control part  3 , a low-speed volume  4  corresponding to the first volume, and a high-speed volume  5  corresponding to the second volume, and the control part  3  comprises a memory  6 . 
     For example, the low-speed volume  4  can be constructed by an SATA (serial AT attachment) disk, an SCSI (small computer system interface) disk or the like. For example, the high-speed volume  5  can be constructed by an FC disk (fiber channel disk). Generally, performance and cost drop in the order of FC disk, SCSI disk, SATA disk. Furthermore, an SAS (serial attached SCSI) disk can also be used. Furthermore, disks that can be used are not limited to these disks; equivalents of FC disks, SCSI disks, SATA disks, SAS disks and the like, and storage devices that will be developed in the future, can also be used. For example, the disks used are not limited to hard disk drives; there are also cases in which the low-speed volume  4  and high-speed volume  5  can be respectively constructed using semiconductor memory drives, optical disk drives or the like. 
     The low-speed volume  4  holds all of the data utilized by the host  2 , and the high-speed volume  5  stores only the portion of the data that is relatively new among the data stored in the low-speed volume  4 . As will be described later, a storage period (life tag) is set beforehand is the data that is stored in the high-speed volume  5 , and data for which this storage period has elapsed is erased from the high-speed volume  5 . Accordingly, the data that is erased from the high-speed volume  5  is stored only in the low-speed volume  4 . 
     The control part  3  processes data access requests from the host  2 , and controls the overall operation of the storage device  1 . The control part  3  can be constructed by causing the cooperation of a plurality of control packages, or can be constructed as a single controller. 
     An updating bit map table  6 A and a life tag control table  6 B are stored in the memory  6  of the control part  3 . Furthermore, a virtual volume  7  is constructed in the storage space of the memory  6 . The virtual volume  7  is formed in the storage space of the memory  6 , and comprises the same size storage capacity as the low-speed volume  4 . The actual body of the virtual volume  7  is the low-speed volume  4  and high-speed volume  5 . 
     The updating bit map table  6 A is control information which controls whether or not the data that is stored in the storage space of the virtual volume  7  is present in the high-speed volume  5 . The life tag control table  6 B is control information that is used to control the storage period (life tag) that is set beforehand in the virtual volume  7 . The life tag is information which indicates the period for which the data is to be stored in the high-speed volume  5 . For example, this life tag can be set in stages such as 1 day, 1 week, 1 month or the like for each virtual volume  7 . In other words, the data stored in a certain virtual volume  7  can be held in the high-speed volume  5  for one day, and the data stored in another virtual volume  7  can be held in the high-speed volume  5  for one week. In  FIG. 1 , only a single virtual volume  7  is shown for convenience of description; however, the storage device  1  may comprise a plurality of virtual volumes  7 . 
     In addition to data, an updating segment control table  8  can be stored in the high-speed volume  5 . For example, this updating segment control table  8  can be constructed by associating the segment (data storage unit) positions in the high-speed volume  5  updated by the host  2 , the segment positions in the low-speed volume  4  where data corresponding to these updating segments is stored, the updating time, the storage period (life tag) in the high-speed volume  5  and the like. Furthermore, it is not necessary that this data be controlled by a single table; the data can also be controlled by causing a plurality of tables to cooperate. Furthermore, all or part of the updating segment control table  8  may be stored in the memory  6 . 
     Next, the operation of the present embodiment will be described. First, the storage device  1  provides a virtual volume  7  to the host  2 . The host  2  recognizes the virtual volume  7  as a physical disk. The application  2 A of the host  2  issues write commands to the virtual volume  2  (S 1 ). 
     When the control part  3  of the storage device  1  receives a write command from the host  2 , the control part  3  temporarily stores the write data transmitted from the host  2  in the memory  6 , and sends back a completion of writing to the host  2 . The control part  3  first writes the write data into the high-speed volume  5  (S 2 ), and then also writes this write data into the low-speed volume  4  at a specified timing (S 3 ). Here, write data is written into the low-speed volume  4  in the same position as the position in the virtual volume  7 . Write data is written into the high-speed volume  5  regardless of the position in the virtual volume  7 . 
     When write data is written into the high-speed volume  5 , the updating bit map table  6 A sets a flag for the segment that is updated by this write data. This flag is information which indicates that the data of this segment is present in a specified position in the high-speed volume  5 . The segment in which the write data is stored and the life tag associated with this write data are respectively registered in the updating segment control table  8  in the high-speed volume  5 . 
     The control part  3  periodically refers to the updating segment control table  8 , and detects data for which the storage period has expired among the data stored in the high-speed volume  5 . Then, the control part  3  erases the data for which the storage period has elapsed from the high-speed volume  5  (S 4 ). Furthermore, the data need not be physically erased; it is sufficient if the data is made logically invalid. Specifically, the segments that are controlled by the updating bit map table  6 A can be invalidated, and these segments can be used to store other new write data by allowing overwriting. 
     Thus, in the present embodiment, write data from the host  2  can be stored in the high-speed volume  5  for a preset storage period, and data for which the storage period has elapsed can be erased from the high-speed volume  5  and stored only in the low-speed volume  4 . In other words, from the time that write data is received until the time that the storage period has elapsed, this write data is stored in both the low-speed volume  4  and high-speed volume  5 , and after the storage period has elapsed, this write data is stored only in the low-speed volume  4 . 
     Accordingly, only data with a high utilization frequency can be stored in the high-speed volume  5 , so that the response characteristics for data with a high utilization frequency can be improved. Furthermore, write data is written into both the low-speed volume  4  and high-speed volume  5 , and data with a low utilization frequency is erased from the high-speed volume  5  after the storage period has elapsed; accordingly, there is no bother of writing data with a low utilization frequency into the low-speed volume  4  alone. 
     Furthermore, since the data life cycle can be controlled within the storage device  1 , there is no need to install new software or the like on the side of the host  2 . Moreover, there is no need for the user to confirm the utilization frequency and select data that is the object of movement, or to issue an instruction to move the selected data to another volume; accordingly, easy and effective data life cycle control can be realized. The present embodiment will be described in greater detail below. 
     1. First Embodiment 
       FIG. 2  is a block diagram showing an overall outline of a storage system containing a storage device  100 . As will be described later, this storage system can be constructed so that this system contains one or more hosts  10 , and one or a plurality of storage devices  100  and  200 . 
     For example, hosts  10  can be roughly divided into so-called open type hosts and main frame type hosts. Examples of open type hosts include sever machines in which a common OS (operating system) such as Windows (registered trademark), UNIX (registered trademark) or the like is installed, and which access the storage device  100  via a relatively all-purpose communications protocol such as FC (fiber channel), iSCSI (internet SCSI), TCP/IP (transmission control protocol/internet protocol) or the like. Examples of main frame type hosts include main frame machines which access the storage device  100  via a communications protocol such as FICON (Fiber Connection: registered trademark), ESCON (Enterprise System Connection: registered trademark), ACONARC (Advanced Connection Architecture: registered trademark), FIBARC (Fiber Connection Architecture: registered trademark) or the like. 
     For example, the host  10  is connected to the storage device  100  via a communications network CN 1  which may contain a metal cable, optical fiber cable, switch or the like. For example, the host  10  can be constructed so that this host comprises one or a plurality of HBAs (host bus adapters)  11 , an input/output (I/O) control program  12 , and an application program group (shown as “application group” in the figure). In  FIG. 1 , for convenience of description, only a single host  10  is shown; however, a plurality of hosts may be provided. Furthermore, open type hosts and main frame type hosts may be mixed. 
     Here, each HBA  11  transmits and receives data on the basis of a specified protocol. For example, the I/O control program  12  is a driver program that controls the data input/output performed using the HBAs  11 . The application program group  13  is an email serving program or a program such as data base control software, a file system or the like, and respectively provides a specified information processing service to client terminals not shown in the figures. 
     The control terminal  20  is a device which is used to collect various types of information for the storage device  100 , and to send necessary commands to the storage device  100  via a service processor (SVP)  180  described later. For example, the control terminal  20  is connected to the SVP  180  via a communications network CN 2  such as an LAN (local area network) or the like. For instance, the control terminal  20  comprises a GUI (graphical user interface) based on a web browser, and performs the collection of various types of information and the input of commands by logging into a WWW (world wide web) server provided by the SVP  180 . In the present embodiment, for example, life tag setting work is performed via the control terminal  20 . Furthermore, the present invention is not limited to cases where control is performed via the control terminal  20 ; control can also be performed from the host  10 . 
     For example, the storage device  100  can be constructed so that this storage device comprises a plurality of CHAs  110 , a plurality of DKAs  120 , a cache memory  130 , a shared memory  140 , a connection control part  150 , a storage part  160 , and an SVP  180 . 
     A plurality of CHAs  110  can be installed in the storage device  100 . The respective CHAs  110  are control packages that control data transfer with the respective hosts  10 . Each CHA  110  comprises a plurality of communications ports  111 , and can be connected with one or more hosts  10 . Each CHA  110  can separately control data transfer with a plurality of hosts  10 . Furthermore, one CHA  110  can control data communications with a second storage device  200  positioned on the outside. 
     A plurality of DKAs  120  can be installed in the storage device  100 . Each DKA  120  can respectively control data transfer with the storage part  160 . For example, each DKA  120  can access respective disk drives  171 , and can read out data or write data, by converting logical block addresses (LBAs) designated by the host  10  into physical disk addresses. 
     The cache memory  130  is a memory that stores write data that is written in from the host  10  and read data that is read out from the host  10 . For example, the cache memory  130  can be constructed by a volatile or nonvolatile memory. In cases where the cache memory  130  is constructed so as to include a volatile memory, it is desirable that memory backup be performed by a battery power supply or the like not shown in the figures. 
     For example, the cache memory  130  can be constructed by a read cache region and a write cache region. For example, the write cache region may include a cache aspect and an NVS (non-volatile storage) aspect, so that the write data is stored in multiplex storage (redundant storage). 
     The shared memory (also called a control memory)  140  can be constructed by (for example) a nonvolatile memory; however, this shared memory can also be constructed by a volatile memory. For example, control information, management information and the like are stored in the shared memory  140 . Information such as this control information and the like can be controlled by multiplex control in a plurality of memories  140 . 
     The shared memory  140  and cache memory  130  can be respectively constructed as separate memories, or the cache memory  130  and shared memory  140  can be disposed inside the same memory package. Furthermore, a portion of one memory can be used as a cache region, and another portion of this memory can be used as a control region. In other words, the shared memory and cache memory can also be constructed as the same memory of memory group. 
     The connection control part  150  connects the respective CHAs  110 , the respective DKAs  120 , the cache memory  130  and the shared memory  140  to each other. As a result, all of the CHAs  110  and DKAs  120  can separately access the cache memory  130  and shared memory  140 . For example, the connection control part  150  can be constructed as an ultra-high-speed cross bar switch or the like. 
     Furthermore, as will be described later, the CHAs  110 , DKAs  120 , cache memory  130  and shared memory  140  can be concentrated in one or a plurality of controllers. 
     The storage part  160  can be constructed so as to comprise numerous disk drives  171 . The storage part  160  can disposed inside the same housing together with the controller parts such as the respective CHAs  110  and respective DKAs  120 , or can be disposed inside another housing separate from the controller parts. 
     For example, the storage part  160  can be constructed so that a plurality of different types of disk drives  171  are mixed. Examples of disk drives  171  that can be used include FC disks (fiber channel disks), SCSI (small computer system interface) disks, SATA (serial AT attachment) disks and the like. Furthermore, the types of disks used are not limited to the abovementioned disks; storage devices comparable to the disk drives shown as examples, or storage devices that may be developed in the future may also be used in some cases. 
     A plurality of parity groups (also called RAID groups) can be disposed in the storage part  160 . The respective parity groups  172  are respectively constructed by the same type of physical disks  171 . Specifically, certain parity groups  172  are constructed only from FC disks, while other parity groups are constructed only from SATA disks. 
     Furthermore, details will be described later; however, one or more logical volumes (also called LDEVs)  173  can be disposed in the logical storage regions respectively provided by the respective parity groups  172 . By associating logical volumes  173  with LUs (logical units)  174 , the open type host  10  can recognize and utilize these volumes as physical storage devices. Furthermore, the volumes that are the object of access by the open type host  10  are LUs; however, the object of access of the main frame type host  10  is logical volumes (LDEVs). 
     The memory resources used by the storage device  100  need not all be present within the storage device  100 . As will be described later, the storage device (which may also be called the first storage device)  100  can incorporate and utilize the memory resources of the second storage device  200  located outside the storage device  100  as though these memory resources were its own memory resources. 
     For example, the SVP  180  can be respectively connected to the respective CHAs  110  and respective DKAs  120  via an internal network CN 3  such as an LAN or the like. The SVP  180  collects various states inside the storage device  100 , and provides these states to the control terminal  20  either “as is” or after processing. Furthermore, the SVP  180  can also register data input from the control terminal  20  in various tables T inside the shared memory  140 . 
     For example, the second storage device  200  can be constructed so that this storage device comprises a controller  210  and a disk drive  220 . The controller  210  respectively controls the exchange of data with external devices (host  10  and storage device  100 ), and the exchange of data with the disk drive  220 . The second storage device  200  may have substantially the same construction as the storage device  100 , or may have a different construction from the storage device  100 . 
     For example, the second storage device  200  is directly connected to the storage device  100  via a communications network CN 4  such as an SAN (storage area network) or the like. In concrete terms, as is shown in  FIG. 3 , the external communications port  111 B of the storage device  100  and the target port  211  of the second storage device  200  are connected via the communications network CN 4  so that two-way data communications are possible. Furthermore, the second storage device  200  can perform the reading or writing of data from or into the disk drives  220  in response to read requests or write requests from the storage device  100 . 
       FIG. 3  is a structural explanatory diagram focusing on the storage structure of the storage device  100 . The storage structure of the storage device  100  can be constructed by a PDEV (physical device)  171  which is a physical disk, a VDEV (virtual device)  172  which is a virtual storage region provided by a plurality of PDEVs  171  formed into a group, and an LDEV (logical device)  173  set in this VDEV  172 . Here, the PDEVs  171  correspond to the disk drives  171  in  FIG. 2 , and the VDEVs  172  correspond to the parity groups  172  in  FIG. 2 . 
     Here, LUNs (logical unit numbers) are respectively assigned to several logical volumes (LDEVs), and these are recognized as LUs  174  by the open type host  10 . The host  10  respectively accesses certain logical volumes (LUs  174 ) that have access authorization via the target port  111 A. The target port  111 A corresponds to the communications port  111  provided by the respective CHAs  110  in  FIG. 2 . 
     A plurality of LDEVs  173  can be respectively disposed in the VDEVs  172 . One LDEV  173  can be associated with one LU  174 , or a plurality of LDEVs  173  can be associated with one LU  174 . Alternatively, a plurality of LDEVs  173  disposed in respective separate VDEVs  172  can be associated with one LU  174 . 
     The VDEV “#  0 ” and VDEV “#  1 ” shown on the right side of  FIG. 3  are virtual intermediate devices, and the actual storage regions are present inside the second storage device  200 . In other words, the storage structure of the second storage device  200  can also be constructed so as to comprise PDEVs  220 , VDEVs  230 , and LDEVs  240 . The LDEVs  240  are associated with LUs  250 . The LDEVS “#  0 ” and “#  1 ” as real volumes of this second storage device  200  are respectively associated with the virtual intermediate devices VDEV “#  0 ” and “#  1 ” of the storage device  100 . 
     For example, the disk drives  171  of the storage device  100  can be constructed from high-speed FC disks, and the disk drives  220  of the second storage device  200  can be constructed from low-speed SATA disks. Accordingly, the high-speed volumes produced inside the storage device  100  are high-speed volumes, and the volumes of the second storage device  200  are low-speed volumes. 
     In the present embodiment, the optimal disposition of data can be achieved by effectively utilizing the high-speed volume which is high-speed within the storage device  100  and the low-speed volume which is low-speed within the second storage device  200 . Furthermore, a construction in which both a high-speed volume and low-speed volume are disposed inside the storage device  100 , or a construction in which both a high-speed volume and low-speed volume are disposed outside the storage device  100  may be used. 
       FIG. 4  is a schematic structural diagram focusing on the main construction of the storage device  100 . The controller  101  of the storage device  100  concentrates the control functions of both the respective CHAs  110  and respective DKAs  120 . The controller  101  controls the overall operation inside the storage device  100 . For example, the controller  101  can comprise a CPU  102 , timer  103 , cache memory  130  and shared memory  140 . Furthermore, in  FIG. 4 , for convenience of description, the cache memory  130  and shared memory  140  are not distinguished, but are shown as a memory  130 / 140 . 
     For example, a mapping table T 1 , life tag setting file T 2 , life tag definition table T 3  and updating bit map table T 4  can be respectively stored in the memory  130 / 140 . The mapping table T 1  is a table that controls the association of real volumes with respective LUs (virtual volumes described later). The life tag setting table T 2  is a table that is used to set life tags that indicate the data storage periods for respective LUs. The life tag definition table T 3  is a table that is used to define the periods indicating the set life tags. The updating bit map table T 4  is a table provided for each LU, which indicates which data is stored in high-speed FC volumes  320  and the like. Furthermore, details of the respective tables T 1  through T 4  will be further described later. 
     A plurality of virtual volumes  310  and  311  can be constructed in the memory  130 / 140 . The storage space of the memory  130 / 140  (especially the cache memory  130  for example) is controlled by being divided into segments of specified amounts, so that the respective virtual volumes  310  and  311  are respectively constructed from numerous segments. The respective virtual volumes  310  and  311  respectively have the same storage capacities as the low-speed SATA volumes  330  and  331  provided by the second storage device  200 . These SATA volumes respectively correspond to the respective LDEVs  240  “#  0 ” and “#  1 ” in  FIG. 3 . 
     The storage device  100  comprises an FC volume  320 . This FC volume  320  corresponds to the LDEV  172  “#  2 ) in  FIG. 3 . The FC volume  320  is respectively associated with a plurality of virtual volumes  310  and  311 . In addition to data storage regions (indicated as “updating segments” in  FIG. 4 ), an updating segment control table T 5  is stored in the FC volume  320 . Details of the updating segment control table T 5  will be described later; however, this is a table that controls the correspondence relationship, storage periods and the like of the data stored in the FC volume  320  and the data stored in the SATA volumes  330  and  331 . 
     In  FIG. 4 , the file system  13 A of the host  10 A utilizes the virtual volume  310 , and the DBMS (data base management system)  13 B of the host  10 B utilizes the second virtual volume  311 . Furthermore, as was described above, the first virtual volume  310  is constructed from the first SATA volume  330  and FC volume  320 , and the second virtual volume  311  is constructed from the second SATA volume and FC volume  320 . 
     The detailed operation will be further described later; however, in cases where the hosts  10 A and  10 B write data into the virtual volumes  310  and  311 , this write data is temporarily stored in the memory  130 / 140  (especially the cache memory  130  for example), and is then written into the FC volume  320 . Then, considering the load on the storage device  100  and the like, the write data is also written into the SATA volumes  330  and  331  at a specified timing. Here, the write positions in the virtual volumes  310  and  311  are the same as the write positions in the SATA volumes  330  and  331 . 
     The data that is stored in the FC volume  320  is present in the FC volume  320  until the storage periods preset for each of the virtual volumes  310  and  311  have elapsed. The data for which the storage period has elapsed is erased from the FC volume  320 , and is stored only in the SATA volumes  330  and  331 . 
     The desired data is read out from the SATA volumes  330  and  331  and provided to the hosts  10 A and  10 B only in cases where the desired data is not stored in the FC volume  320 . As a result, the hosts  10 A and  10 B can mainly read and write data utilizing the high-speed FC volume  320 . 
       FIG. 5  is an explanatory diagram showing an example of the construction of the mapping table T 1 . For example, the mapping table T 1  can be stored in the shared memory  140 . Furthermore, the same is also true of the respective tables described below; however, all or part of the mapping table T 1  can also be copied into the local memories inside the respective CHAs  110 . 
     For example, the mapping table T 1  can be constructed by associating the LUNs, the LDEV numbers and LDEV sizes (slot numbers) associated with these LUNs, the VDEV numbers and VDEV sizes associated with these LDEVs, the device types of these LDEVs, and the path information for the disk drives in which these VDEVs are formed. As is shown in  FIG. 5 , in cases where the volumes of the external second storage device  200  are incorporated and used, the paths used to access the volumes of the second storage device  200  are set in the path information. Furthermore, in cases where volumes inside the storage device  100  are used (the FC volume  320  in the present embodiment), information used to access these internal volumes is set. 
       FIG. 6  is an explanatory diagram which respectively indicates examples of the construction of the life tag setting table T 2  and life tag definition table T 3 . For example, these respective tables T 2  and T 3  can be stored in the shared memory  140 . In the life tag setting table T 2 , for example, the LUNs and life tags are associated. Specifically, for each LUN, respectively different life tags can be set for each virtual volume  310  and  311 . For example, a plurality of levels such as 0, 1, 2, 3 and the like exist for the life tags. 
     For example, the life tag definition table T 3  defines concrete storage periods for each life tag level. For instance, storage periods are respectively defined for each life tag level, such as 1 day in a case where the life tag is “0”, 3 days in a case where the life tag is “1”, 7 days in cases where the life tag is “2”, 30 days in cases where the life tag is “3” and the like. The life tag setting and life tag definition can be respectively set by the user via the control terminal  20 . 
       FIG. 7  is an explanatory diagram which shows an example of the construction of the updating bit map table T 4 . For example, the updating bit map table T 4  can be respectively set for each virtual volume  310  and  311  and each LUN, and can be stored in the shared memory  140 . 
     The respective updating bit map tables T 4  can be constructed (for example) by associating the segment numbers in the cache memory  130 , the FC flags, and the updating segment numbers in the FC volume  320 . 
     Here, the FC flag is information that indicates whether or not the data of the segment in question is present in the FC volume  320 . In cases where “1” is set in the FC flag, this indicates that the data of this segment is stored in the FC volume  320 . In cases where “0” is set in the FC flag, this indicates that the data of this segment is not present in the FC volume  320 . 
     The segment number indicates the storage position of the data in the virtual volumes  310  and  311  constructed in the cache memory  130 . As was described above, the data storage positions in the virtual volumes  310  and  311  are the same as the data storage positions in the respective SATA volumes  330  and  331 . The updating segment number indicates the data storage position in the FC volume  320 . The data storage position (updating segment number) in the FC volume  320  does not coincide with the segment numbers in the virtual volumes  310  and  311 . In order to utilize the storage region of the FC volume effectively, for example, data is stored in order in empty updating segments. 
       FIG. 8  is an explanatory diagram which shows the construction of the updating segment control table T 5 , and which also shows how data for which the storage period has elapsed is erased from the FC volume  320  using the updating segment control table T 5  and the like. 
     For example, the updating segment control table T 5  can be constructed by associating the segment numbers that indicate the storage positions in the FC volume  320  (corresponding to the updating segment numbers in  FIG. 7 ), the LUNs (virtual volume numbers) to which the data stored in these segments belong, the updating segment numbers (corresponding to the segment numbers in  FIG. 7 ) that indicate the storage positions in the SATA volumes  330  and  331  storing the same data as the data stored in these segments, the life tag levels (storage periods) of the data stored in these segments, the time of updating of these segments, and SATA updating bits indicating whether or not the data stored in these segments is also stored in the SATA volumes  330  and  331 . 
     It is not necessary to set the updating time in a year, month and day format; as is shown in  FIG. 8 , it is sufficient if a value counted by the timer  103  is set. The timer  103  increases the count by one increment for each day. Accordingly, by comparing the count values of the timer  103 , it is possible to determined the number of days elapsed from the point in time at which a certain count value was recorded. Furthermore, the updating date can also be registered using a year, month and day format. 
     The controller  101  refers to the updating segment control table T 5  either periodically or irregularly, and compares the storage time indicated by the life tag with the time elapsed to the current point in time for the respective segments (only segments in which data is stored) in the FC volume  320 . It is sufficient if this comparison is performed at least once a day. Furthermore, the comparison table T 6  shown in  FIG. 8  is shown for convenience of description; it is also possible to perform data cleaning processing without producing a comparison table T 6 . 
     For example, when reference is made to the updating segment control table T 5 , the data stored in the segment “#0001” of the FC volume  320  belongs to the virtual volume  330  “#  0 ”; accordingly, “1” is associated as the life tag level. The storage period in the case of a life tag level of “1” is 3 days. Furthermore, when this data was stored in the segment “#0001” of the FC volume  320 , it is assumed that the count value of the timer  103  was “250”. 
     It is assumed that the count value of the timer  103  is currently “254”. Thus, a period of 4 days has already elapsed since the updating of the data stored in segment “#0001” of the FC volume  320 . However, the storage period of this data is set at 3 days. Accordingly, the controller  101  invalidates the updating segment of the updating bit map table T 4  (corresponding to the segment of the FC volume), and permits overwriting. As a result, other new data can be stored in the segment storing data for which the storage period has elapsed. 
       FIG. 9  is a flow chart showing an outline of the updating processing. For example, this processing is executed by the CHA  110 ; however, in the following description, the main body of the operation is described as being the controller  101 . 
     The controller  101  receives a write command from the host  10  (S 11 : YES), and judges whether or not any empty capacity for storing write data is present in the cache memory  130  (S 12 ). If the empty capacity required for the storage of the write data is not present (S 12 : NO), the controller  101  causes the host  10  to wait until this empty capacity is formed. As will be described in the destage processing described later, the data stored in the cache memory  130  is successively written into the FC volume  320 , and the data written into the FC volume  320  is erased from the cache memory  130 . Accordingly, while the host  10  is being caused to wait for the transmission of write data, the data in the cache memory  130  is written into the FC volume, so that the empty capacity is increased. 
     Then, when the required empty capacity is formed (S 12 : YES), the controller  101  allows the host  10  to transmit write data, and receives the write data transmitted from the host  10  (S 13 ). After the controller  101  stores the write data received from the host  10  in the cache memory  130  (S 14 ), the controller  101  notifies the host  10  of the completion of the write command (S 15 ). Specifically, at the point in time at which the controller  101  redundantly stores the write data in the cache memory  130 , the controller notifies the host  10  of the completion of the write command, and the writing of the write data into the volume is performed at a different timing. This mode in which the timing at which the write data is written into the volume and the timing at which the host  10  is notified of the completion of the command are thus different can be called the “asynchronous write mode”. By using this asynchronous write mode, it is possible to release the host  10  early from writing processing. 
       FIG. 10  is a flow chart showing an outline of the destage processing. For example, this processing can be executed by a DKA  120 ; in the following description, however, the main body of the operation will be described as the controller  101 . 
     On the basis of a write command, the controller  101  specifies the segment that is to be updated by the write data (S 21 ). For example, the segment that is to be updated can be specified from the LUN (virtual volume number) into which the write data is written and the LBA in which the write data is to be stored. 
     The controller  101  refers to the updating bit map table T 4  associated with the LU (virtual volume) into which the write data is to be written (S 22 ), and judges whether or not the data of the segment that is the object of updating is present in the FC volume  320  (S 23 ). 
     If the data of the segment that is the object of updating is not stored in the FC volume  320  (S 23 : NO), the controller  101  reads out old data from the SATA volume corresponding to the virtual volume that is the object of updating, joins this old data and the write data, and produces the full data of the segment that is the object of updating (S 24 ). 
     Furthermore, in cases where the old data is stored in the cache memory  130 , there is no need to read out data from the SATA volume; the data stored in the cache memory  130  may be used. In ordinary cases, since reference processing is executed prior to updating processing, and old data is read out from the cache memory  130 , the possibility of a cache hit is high. In cases where the old data is stored in the cache memory  130 , there is no need to access the low-speed SATA volume and read out data, so that the response characteristics are improved. 
     Next, the controller  101  ensures a specified number of segments that are not being used in the FC volume  320 , and specifies (confirms the updating segment number in which updated data is to be stored (S 25 ). 
     The controller  101  registers the specified updating segment number in the updating bit map table T 4 , and sets the FC flag as “1” for this updating segment (S 26 ). Next, the controller  101  stores the updated data in the updating segment registered in the updating bit map table T 4  (S 27 ), and updates the updating segment control table T 5  (S 28 ). 
     On the other hand, in cases where data of the segment that is the object of updating is present in the FC volume  320  (S 23 : YES), the controller  101  specifies the segment number that is the object of updating (S 29 ), and stores the updated data in this specified segment (S 30 ). Furthermore, in S 30 , the controller  101  rewrites the updating date of this segment to the current date (most recent count value of the timer  103 ), and updates the updating segment control table T 5  (S 28 ). 
     Thus, after write data received from the host  10  is stored in the high-speed FC volume  320 , the controller  101  judges whether or not the SATA volume can be updated (S 31 ). The writing of data into the FC volume  320  and the writing of data into the SATA volume can be performed simultaneously, or write data can be written into the SATA volume at a shifted timing. For example, the controller  101  can update the SATA volume at a timing at which the processing burden on the storage device  100  is relatively small. 
     In cases where the SATA volume can be updated (S 31 : YES), the controller  101  writes the updated data into a specified storage position in the SATA volume corresponding to the virtual volume that is the object of updating (S 32 ), sets “1” in the SATA updating bit corresponding to this segment (S 33 ), and updates the updating segment control table T 5 . Then, the controller  101  releases the storage region in which the write data was stored in the cache memory  130  (S 34 ). As a result, other data can be overwritten in the storage region in which this write data was stored. 
     On the other hand, in cases where the SATA volume cannot be updated because of a heavy processing burden on the storage device  100  or the like (S 31 : NO), the controller  101  sets “0” in the SATA updating bit corresponding to the updated segment in the FC volume  320  (S 35 ), erases the write data stored in the cache memory  130 , and releases the storage region (S 34 ). 
     Thus, in the destage processing, the write data received from the host  10  is first stored in the high-speed FC volume  320 , and the write data is also stored in the SATA volume either substantially simultaneously with the storage in the FC volume  320 , or with some delay following this storage. Furthermore, in cases where the write data is stored in the FC volume  320 , regardless of whether or not the write data is stored in the SATA volume, the write data in the cache memory  130  is erased, so that an empty capacity is produced. 
       FIG. 11  is a flow chart which shows an outline of the reference processing. When the controller  101  receives a read command from the host  10  (S 41 : YES), the controller  101  specifies the segment to which reference is to be made by analyzing the read command (S 42 ). For example, the reference segment can be specified by means of the LUN (virtual volume number) that is the object of reference and the segment number that is the object of reference. 
     The controller  101  refers to the updating bit map table T 4  that is associated with the virtual volume that is the object of reference (S 43 ), and judges whether or not the data of the segment for which read-out was requested is present in the FC volume  320  (S 44 ). In cases where the data requested by the host  10  is stored in the FC volume  320  (S 44 : YES), the controller  101  specifies the segment number that is the object of reference (S 45 ), and reads out the data from the segment of the FC volume  320  (S 47 ). 
     On the other hand, in cases where the data requested by the host  10  is not stored in the FC volume  320  as a result of the execution of cleaning processing (described later) (S 44 : NO), the controller  101  reads out the data requested by the host  10  from the SATA volume (S 47 ). 
     After the controller  101  stores the data read out from either the FC volume  320  or SATA volume in the cache memory  130 , the controller  101  transmits this data to the host  10  (S 48 ). Furthermore, the controller  101  notifies the host  10  that the processing of the read command has been completed (S 49 ). 
     Thus, in reference processing (read command processing), in cases where the requested data is stored in the FC volume  320 , the controller  101  reads out the data from the FC volume  320  and provides this data to the host  10 . 
       FIG. 12  is a flow chart showing an outline of the cleaning processing. The controller  101  performs cleaning processing at least once a day. In the present embodiment, since the minimum storage period of the life tag is 1 day, it is sufficient if cleaning processing is performed once a day. For example, the controller  101  performs cleaning processing in accordance with the minimum storage period of the life tag. 
     The controller  101  refers to the updating segment control table T 5 , and calculates the number of days elapsed up to the current time for each of the respective updating segments stored in the FC volume  320  (S 51 ). The number of days elapsed can be determined by subtracting the updating date of the segment (count value at the time of updating) from the current date (count value of the timer). 
     The controller  101  compares the number of elapsed days calculated for the segment with the storage period set for the data stored in the segment, and judges whether or not the storage period has elapsed (S 52 ). In cases where the storage period has already elapsed (S 52 : YES), the controller  101  judges whether or not the SATA updating bit associated with the segment is set as “1” (S 53 ). 
     In cases where “1” is not set in the SATA updating bit (S 53 : NO), this indicates a case in which the data that is the object of cleaning is not stored in the SATA volume; accordingly, the controller  101  refers to the LUN and segment of the SATA volume constituting the object of data updating (S 54 ), and writes the data that is the object of erasing into the segment of this confirmed SATA volume (S 55 ). On the other hand, in cases where “1” is set in the SATA updating bit (S 53 : YES), the data that is the object of erasing is stored in the SATA volume; accordingly, S 54  and S 55  are skipped. 
     Next, the controller  101  invalidates the segment storing the data that is the object of erasing in the updating bit map table T 4  corresponding to the data that is the object of erasing (S 56 ), and resets the FC flag corresponding to this segment to “0” (S 57 ). As a result, other write data can be overwritten in the segment of the FC volume  320  in which the data that is the object of erasing is stored. 
     The controller  101  checks whether or not all of the updating segments of the FC volume  320  have been inspected (S 58 ), and in cases where the inspection of all of the updating segments has not been completed (S 58 : NO), the processing moves to the next segment of the updating segment control table T 5  (S 59 ), and returns to S 51 . Then, when inspection has been completed for all of the updating segments registered in the updating segment control table T 5  (S 58 : YES), this processing is ended. 
     Since the present embodiment is constructed as described above, this embodiment possesses the following merits. In the present embodiment, a construction is used in which data is respectively written into both a high-speed FC volume  320  and low-speed SATA volumes  330  and  331  during data updating, and data is held in the high-speed FC volume  320  only for a storage period that is set in advance by a life tag. 
     Accordingly, data with a high utilization frequency can be held in the FC volume  320 , so that a rapid response to subsequent data access is possible. Furthermore, after the storage period has elapsed, data is held only in the low-speed, inexpensive SATA volumes  330  and  331 , so that the high-speed FC volume  320  is prevented in advance from becoming filled with unnecessary non-urgent data, thus making it possible to maintain high-speed volume response characteristics. 
     In the present embodiment, since data for which the storage period has elapsed is erased from the high-speed FC volume  320  in the storage device  100 , data disposition corresponding to the utilization frequency (utilization value) of the data can be realized without adding any special function to the host  10 . Accordingly, the user need not designate the data that is the object of movement or the like as in conventional data migration, so that the convenience of the system is improved. Furthermore, data that is the object of movement does not flow on the communications network CN 1  that connects the host  10  and storage device  100 , so that an increase in traffic can be prevented. 
     In the present embodiment, since a construction is used in which respective life tags are set for each virtual volume  310  and  311 , life tags can be automatically set for (e.g.) each application using the virtual volumes, or each host using the virtual volumes. 
     In the present embodiment, virtual volumes  310  and  311  are respectively constructed in a plurality of SATA volumes  330  and  331  in association with a single FC volume  320 . Accordingly, a plurality of virtual volumes  310  and  311  can be constructed by means of an FC volume  320  with a small storage capacity compared to the total storage capacity of the respective SATA volumes  330  and  331 . As a result, the response characteristics and the like of the storage device  100  can be improved suing an FC volume  320  with a relatively small storage capacity. 
     In the present embodiment, the levels of the life tags can be set in stages; accordingly, for example, appropriate storage periods can be set in accordance with the type of application programs using the virtual volumes. Furthermore, the setting of life tags and the definition of the contents of these life tags can be set manually by the user via the control terminal  20 , so that storage periods can be freely set in accordance with the use configurations of the user. 
     2. Second Embodiment 
     A second embodiment will be described with reference to  FIGS. 13 through 18 . In the present embodiment, life tags are set in the host  10  in file units or directory units. Furthermore, the storage device  100  performs data re-disposition (erasing of data from the high-speed volume) in accordance with life tags set by the host  10 . 
     As is shown in the overall schematic structural diagram in  FIG. 13 , the host  10 C in the present embodiment (like the hosts  10 A and  10 B in the abovementioned embodiments) comprises a life tag setting part  14  in addition to an I/O control program  12 C, application group  13 C and the like. 
     The life tag setting part  14  has a function that is used to set storage periods in stages in file units or directory units. For example, all or part of this function can be disposed inside the application group  13 C. Furthermore, in the present embodiment, since life tags are set in the host  10 C, a life tag setting table T 2  is not stored in the memory  130 / 140  of the storage device  100 . 
       FIG. 14  is a model diagram which shows how communications are performed between the host  10 C and storage device  100  during updating processing. As one example, a higher application program (hereafter referred to as a higher application)  15  can be disposed in the host  10 . For example, the higher application  15  is document creating software, graphic creating software or the like. 
     For example, when the higher application  15  requests the updating of a file, the file system  13 C which is one example of an application group transfers the file data that is the object of updating to the I/O control program  12 C. In the present embodiment, for example, the I/O control program  12 C can be constructed as an FCP_SCSI driver program. 
     The I/O control program  12 C issues a write command (FCP_CMND (write)) to the controller  101  of the storage device  100 . When the controller  101  receives a write command, the controller  101  checks whether or not any empty capacity is present in the cache memory  130 ; in cases where such an empty capacity can be confirmed, the controller  101  notifies the host  10 C that preparations for the reception of write data have been completed (FCP_XFER_READY). 
     When the host  10 C receives this notification, the host  10 C transmits file data to the storage device  100  (FCP_DATA). In cases where the controller  101  normally receives file data and stores this data in the cache memory  130 , the controller  101  notifies the host  10 C of the completion of processing of the write command (FCP_RSP). In the present embodiment, as will be described later, a life tag is embedded in the write command that is issued by the host  10 C. 
       FIG. 15  is a model diagram which shows one example in which the life tags are set in file units or directory units. For example, as is shown in  FIG. 15  ( a ), the user displays a file tree structure on the terminal screen, and selects the desired file or directory using a pointing device such as a mouse or the like. The user displays a life tag setting menu M 1  for the selected file or directory, and sets a life tag of the desired level. 
     In  FIG. 15 , it is assumed that the user has selected the directory “User  1 ”, and as set a life tag of level  3 . Consequently, as is shown in  FIG. 15  ( b ), life tags of level  3  are set for all of the files “file  1 ” through “file  4 ” contained in this directory “User  1 ”. 
     Furthermore, in  FIG. 15  ( b ), for convenience of description, the life tag levels are shown as being visualized. However, the present invention is not limited to this; for example, it would also be possible to use a construction in which the levels of the life tags are confirmed by means of a window or the like that displays file attributes. Furthermore, the life tag setting method is not limited to the example described above; various methods can be employed. For example, in cases where files are stored by the higher application  15  or the like, a construction may be used in which desired life tags are set via the user interface of the higher application  15 . Furthermore, a construction in which life tags of the same level are uniformly set for all of the files contained in the directory selected by the user is shown as an example. However, the present invention is not limited to this; for example, the system can also be constructed so that the setting of life tags is prohibited for specified files such as system hidden files, files set beforehand by the user or the like. 
       FIG. 16  is an explanatory diagram which shows how life tags are embedded in the write commands. In cases where the higher application  15  performs file updating, a file control function indicating “updating” is input for the file system  13 C from the higher application  15 . At this point in time, a life tag is not set for the file that is to be updated. 
     For example, the file system  13 C performs file control by associating file discriminating information, file names, file data storage destination addresses, file attribute information, life tags and the like for each file. When a file control function is input from the higher application  15 , the file system associates a life tag with the file data that is to be updated, produces an I/O control function for updating use, and inputs this into the I/O control program  12 C. 
     For example, this I/O control function for updating use may contain the LUN (virtual volume number) in which the file data that is the object of updating is stored, the starting address (LBA: logical block address) of the file data that is to be updated, the LBA length, the level of the life tag and the file data that is to be updated. 
     Then, when the I/O control program  12 C receives the updating I/O control function from the file system  13 C, this program produces a specified write command (FCP_CMND (write)), and transmits this command to the storage device  100 . 
       FIG. 17  is an explanatory diagram which shows the construction of the write command. The life tag contained in the I/O control function can be embedded in the write command by various methods. For example, the life tag can be stored in at least one of the regions D 331 , D 334   a  and D 334   g  described later. 
     This will be described in order from the lower side of  FIG. 17 . The frame format D 3  used in a fiber channel (FCP) can include the regions D 31  through D 35 . The region D 31  is an SOF (start of file) region used to discriminate the head of the frame. The region D 32  is a frame header region. The region D 33  is a data field region which accommodates commands and the like. The region D 34  is a CRC regions which is used to accommodate a CRC (cyclic redundancy check) code that checks the data with the frame header region D 32  and data field region D 33 . The region D 35  is an EOF (end of file) region which is used to discriminate the end of the frame. 
     The data field region D 33  can be constructed from the regions D 331  through D 335 . The region D 331  is an optional header region, and is provided in cases where the presence of this region is indicated by the frame header region D 32 . In the optional header region D 331 , for example, the expiration time of the transmitted frame, the routing between networks and information used to discriminate the process group, process or the like can be accommodated. In ordinary cases, however, this is not used. 
     The region D 332  is an FCP_LUN region that stores the LUN. The region D 333  is an FCP_CNTL region that stores control information. The region D 334  is an FCP_CDB (command descriptor block) that stores SCSI commands. The region D 335  is an FCP_DL region that stores the data length. 
     The FCP_CDB region D 334  can be constructed from the regions D 334   a  through D 334   h . The region D 334   a  is an operation code region that indicates that this is a write access. The following region D 334   b  is an LUN region that stores the LUN; however, in ordinary cases, this is not used. The region  334   c  is a DPO (disable page out)/FUA (force unit access) region. The region D 334   d  is an LBA region that stores the logical block address (LBA). The region D 334   e  is a reserved region. The region D 334   f  is an LBA length region. The region D 334   g  is a VU (vendor unique) region which accommodates information unique to the vendor. The region D 334   h  is a region that can accommodate reservation information, flag information and the like. 
     Here, the regions that can accommodate life tag information will be examined. First, life tag information cannot be stored in regions that are already being used. The life tags must be set in unused regions. Furthermore, in cases where the type (level) of the life tag is tentatively set as “4”, an empty region of 2 bits or greater is required in order to accommodate the life tag information. Accordingly, the life tag information can be set in at least one region among the regions D 331 , D 334   b  and D 334   g  shown in  FIG. 17 . 
       FIG. 18  us a flow chart which shows an outline of the destage processing of the present embodiment. S 62  through S 75  in the present processing respectively correspond to S 22  through S 35  in  FIG. 10 ; accordingly, a description of these steps will be omitted. 
     In S 61  of the present processing, this step differs from S 21  in  FIG. 10  in that life tag information is extracted from the write command. The extracted life tag is stored in a specified position in the updating segment control table T 5 . 
     Thus, in the present embodiment, life tags can be set in stages on the side of the host  10 C in file units or directory units. Accordingly, even in the case of data that is stored in the same virtual volume, respectively different storage periods can be set. Thus, since life tags can be set in file units or directory units, the disposition of data can be controlled much more in accordance with the utilization frequency, so that the convenience of use is improved. 
     Furthermore, in the present embodiment, a construction is used in which life tags for updated data can be set on the side of the host, so that the storage device can erase data for which the storage period has elapsed from the high-speed volume in accordance with life tags set by the host. Accordingly, even in the case of detailed data control, there is no burden on the host in regard to searching for object data or moving data. Specifically, in the present embodiment, the host need merely set information (life tags) acting as a policy for data control in file units or directory units; the actual data control based on this data control policy is performed in the storage device. Thus, the setting of data control policies and the execution of control based on these data control policies is divided between the host and the storage device, so that detailed data control can be performed without increasing the burden on the host. 
     Furthermore, in the present embodiment, life tag information is embedded using an already prepared command structure; accordingly, the convenience of use of the storage device  100  can be improved while maintaining the existing framework. 
     3. Third Embodiment 
     A third embodiment will be described with reference to  FIG. 19 . In the present embodiment, the life tag setting table T 2 A is expanded, so that life tags can be set even in cases where a plurality of LDEVs are associated with a single LUN. 
     In the life tag setting table T 2 A, a plurality of LDEVs and the life tags for the respective LDEVs are associated for each LUN. Thus, the present invention can be applied in cases where a single LUN (virtual volume) is constructed from a plurality of SATA volumes. 
     4. Fourth Embodiment 
     A fourth embodiment will be described with reference to  FIGS. 20 and 21 . As is shown in the schematic structural diagram in  FIG. 20 , respective FC volumes  320  can be associated with respective virtual volumes  310  in the present embodiment. 
     Thus, by constructing virtual volume  310  by associating respectively different FC volumes  320  with respective SATA volumes  330 , it is possible to increase the proportion of the high-speed storage region in a single virtual volume  310 , so that more data can be stored for a longer time in the FC volumes  320  than in the respective embodiments described above. 
       FIG. 21  shows an example of the construction of the LUN-FC volume correspondence table T 7  used in a case where respective FC volumes  320  are associated with respective virtual volumes (LUNs). As is shown in  FIG. 21  ( a ), in this table T 7 , control is performed so that FC volume numbers are associated with respective LUNs. Furthermore, as is shown in  FIG. 21  ( b ), a plurality of FC volumes can be installed, and each FC volume can be associated with a plurality of virtual volumes. 
     5. Fifth Embodiment 
     A fifth embodiment will be described with reference to  FIG. 22 . In the present embodiment, the updating segment control table T 5  is stored in the memory  130 / 140  (especially the shared memory  140  for example) rather than being stored in the FC volume  320 . 
     Thus, as a result of the updating segment control table T 5  being stored in the memory  130 / 140 , it is possible to store only data in the FC volume  320 , so that the storage region of the FC volume  320  can be utilized more effectively. 
     Furthermore, the present invention is not limited to the embodiments described above. Various additions or alterations may be made by a person skilled in the art within the scope of the present invention. For example, a person skilled in the art can appropriately combine the respective embodiments described above. Furthermore, for example, an NAS (network attached storage) service can be provided by installing a control package mounting an NAS file system (NAS blade) in the storage device. In this case, for example, life tags can be associated with updated files inside the NAS blade.