Patent Publication Number: US-7725611-B2

Title: Method and apparatus for verifying data in a storage system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation application of U.S. Ser. No. 11/025,471, filed Dec. 28, 2004, now abandoned, which is a continuation application of U.S. Ser. No. 10/377,898, filed Feb. 28, 2003, now U.S. Pat. No. 6,842,793, issued Jan. 11, 2005. The present application claims priority upon Japanese Patent Application No. 2002-092685 filed Mar. 28, 2002, which is herein incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method for verifying data in a storage system, a host computer and a storage controller in a storage system. 
   2. Description of the Related Art 
   A storage system in which a host computer and a storage controller such as a disk array device are interconnected via a SAN (Storage Area Network) or other networks for intensive storage operation or other similar purposes have been attracting considerable attention. Storage systems configured as above are now being operated at IDCs (Internet Data Centers) and many other places. Recently, focus has been made on systems that use a storage controller called a NAS (Network Attached Storage) which is provided with a file system and uses a LAN (Local Area Network) as the network. 
   It is often required that the data for database software or other application programs running on a host computer in a storage system configured and operated as described above is in accordance with certain specifications (such a property is hereinafter referred to as “suitability”). Under these circumstances, some application programs are provided with an algorithm for verifying the suitability of the data to be processed. 
   Even if an application program is provided with the above-mentioned algorithm, however, the data suitability may be lost depending on the SAN or other communication path for connecting a host computer to a storage controller or due to an internal process performed by the storage controller. Further, the storage controller is frequently shared by a plurality of host computers. In such a situation, the data suitability may be impaired if, for instance, an application program running on one host computer inadvertently accesses the data of an application program running on another host computer. 
   If, for instance, the suitability of the data to be written into a storage controller is lost in a situation in which an application program is not involved, the storage controller will not be able to recognize such a loss of data suitability and will automatically store the unsuitable data. In this instance, the application program will not recognize the loss of data suitability until it reads the data later. If there is a long time lag between the instant at which the data is written and the instant at which the data is read, data recovery may be difficult to achieve. 
   Even in situations where data is backed up by the storage controller, data recovery win not be achievable if the backed-up data has already lost suitability. Further, if the data suitability is lost in a situation in which an application program is not involved as mentioned above, the cause of the problem is often difficult to specify so that subsequent failure recovery and other similar operations may be rendered difficult to accomplish. 
   The above problem can be solved if the storage controller is configured to verify the data. In storage systems, data stored in the storage controller by an application program is generally provided with additional information such as information added by an operating system (hereinafter referred to as the “OS”) running on a host computer and information about volumes having been logically organized by a host computer. Further, for example, due to the OS, volume management program, etc., the data stored in the storage controller by an application program is not arranged in a manner in which the data on a host computer is arranged for reference by the application program. However, the storage controller would not be able to get hold of the above-mentioned information and arrangement. That is, as far as the traditional storage system scheme is used, the data verification process performed by an application program cannot be performed by the storage controller. If it were to allow the storage controller to accomplish such data verification, it would be necessary to establish a scheme that would enable the storage controller to acquire relevant information from an application program, OS, and volume management program. 
   As a scheme to facilitate the checking procedure for enhancement of data reliability, i.e., RAS (Reliability, Availability, and Serviceability), which is conducted when an application program reads data from or writes data onto a magnetic disk, for example, Japanese Patent Application Laid-open Publication No. 8-263223 discloses a mechanism in which the CPU generates RAS data when an I/O operation is performed by an application program and attaches the RAS data to data to be written onto a magnetic disk, in order to enable a magnetic disk input/output channel and magnetic disk controller to conduct a data check. 
   In the scheme disclosed in the above-mentioned publication, however, the RAS data is independently generated by the CPU and appended to the data to be written. Further, the RAS data does not relate to the data suitability required by an application program. The disclosed scheme is not configured to recognize such information or configuration nor to verify the suitability demanded by individual application programs running on a host computer. 
   SUMMARY OF THE INVENTION 
   The present invention is made to solve the foregoing and other problems, and it is an object of the present invention to provide a data verification method for verifying and assuring data suitability in a storage system with increased accuracy and, more particularly, to offer a method for carrying out, in a storage system, data verification demanded by an application program. 
   It is a further object of the present invention to provide a host computer and storage controller that realize the above-mentioned functionality. 
   According to one aspect of the present invention, which achieves the foregoing and other objects, there is provided a method for verifying data in a storage system, the storage system including a host computer and a storage controller, the storage controller being connected to the host computer for communication therewith, being capable of receiving an input/output request transmitted from the host computer, and, according to the request, being capable of performing a data input/output process to a storage device, the method comprising the steps of: the host computer executing an application program for organizing and managing data to be stored in the storage controller in accordance with a predefined specification; the host computer transmitting area management data to the storage controller, wherein the area management data is for specifying a range of a storage area that is provided in the storage device to be used by the application program; the storage controller receiving the area management data; and the storage controller receiving a data input/output request that is transmitted from the host computer caused by a process performed by the application program, and verifying whether data that is to be processed according to the received data input/output request and to be input/output to/from the storage area used by the application program, which is specified in accordance with the area management data, is organized in accordance with the predefined specification. 
   According to such an aspect of the present invention, it becomes possible to offer a data verification method, a host computer, and a storage controller for verifying and assuring the data suitability in a storage system with increased accuracy. 
   Features and objects of the present invention other than the above will become clear by reading the description of the present specification with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a diagram illustrating the configuration of a storage system according to an embodiment of the present invention; 
       FIG. 2  is a diagram showing an area management table according to an embodiment of the present invention; 
       FIG. 3  is a flowchart depicting processing steps that are performed in an embodiment of the present invention when a host computer transmits an area management table to a storage controller; 
       FIG. 4  is a diagram illustrating a logical device management table according to an embodiment of the present invention; 
       FIG. 5A  is a diagram illustrating a data unit that is used in an embodiment of the present invention when an application program performs a data input/output operation to a logical volume; 
       FIG. 5B  is a diagram showing how a logical volume management program divides a data unit, which is shown in  FIG. 5A , when performing an input/output operation to a storage controller; 
       FIG. 5C  is a diagram showing how the divided data are stored in a logical device; 
       FIG. 6A  is a diagram illustrating a data unit, which is shown in  FIG. 5A , in a SCSI data format; 
       FIG. 6B  is a diagram illustrating the data, which is shown in  FIG. 5B , in a SCSI data format; 
       FIG. 7  is a flowchart depicting data verification processing steps that are performed by a storage controller according to an embodiment of the present invention; and 
       FIG. 8  is a block diagram that shows the configuration of an example of a host computer. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   At least the following matters will be made clear by the explanation in the present specification and the description of the accompanying drawings. 
   =Outline of General Description= 
   A method for verifying data according to an embodiment of the present invention is a method for verifying data in a storage system, the storage system including a host computer and a storage controller, the storage controller being connected to the host computer for communication therewith, being capable of receiving an input/output request transmitted from the host computer, and, according to the request, being capable of performing a data input/output process to a storage device, comprising the steps of: the host computer executing an application program for organizing and managing data to be stored in the storage controller in accordance with a predefined specification; the host computer transmitting area management data to the storage controller, wherein the area management data is for specifying a range of a storage area that is provided in the storage device to be used by the application program; the storage controller receiving the area management data; and the storage controller receiving a data input/output request that is transmitted from the host computer caused by a process performed by the application program, and verifying whether data that is to be processed according to the received data input/output request and to be input/output to/from the storage area used by the application program, which is specified in accordance with the area management data, is organized in accordance with the predefined specification. 
   The “input/output request transmitted from the host computer” is, for instance, a data write request or data read request for the above-mentioned storage device such as a disk drive included in a storage controller or externally connected to the storage controller. The “area management data” is the data registered in an area management table, which is described later. The data verification method according to the present invention verifies, also in the storage controller, whether the data handled by application programs are organized in accordance with a predefined specification. This ensures that the data suitability can be verified and assured with increased accuracy. 
   The data verification method mentioned above may comprise the steps of: the storage controller storing a plurality of algorithms, wherein each of the algorithms is for performing the verification for each of a plurality of application programs running on the host computer; the storage controller specifying storage areas used by each of the application programs in accordance with the area management data transmitted from the host computer; the storage controller receiving a data input/output request transmitted from the host computer caused by a process performed by one of the application programs, and specifying the application program relating to the received data input/output request in accordance with the area management data; and the storage controller verifying, using the algorithm provided for the specified application program, whether data that is to be processed according to the received data Input/output request and to be input/output to/from the storage area, which is specified in accordance with the area management data, is organized in accordance with the predefined specification. 
   Accordingly, it becomes possible to verify, also on the storage controller side, the data handled by different application programs even when a plurality of different application programs run on the host computer. 
   The data verification method described above may comprise the steps of: the host computer transmitting the algorithm from the host computer to the storage controller; and the storage controller receiving and storing the algorithm. 
   The data verification method described above may comprise the step of the host computer transmitting, when a change has been made in the range of the storage area, the area management data reflecting the change to the storage controller. Accordingly, it becomes possible to ensure that also the storage controller can get hold of the latest information about the storage area of the storage device for use by an application program. 
   The storage area in the storage device used by the application program may be an area excluding an area used by control information added by software other than the application program running on the host computer. 
   The area management data may include data for designating a range of the storage area that is provided for the application program as a volume having been logically organized using the storage area of the storage device. 
   The volume may be organized by managing the storage area of the storage device according to a RAID method. 
   The storage device may be provided integrally with the storage controller. Further, the data indicating the result of the verification may be transmitted to the host computer. For example, the storage area may be provided as a logical storage device that is organized in a physical storage region provided by at least one physical storage device. The predefined specification means, for example, that prescribed data is inserted into a prescribed position of the data. The storage controller may be connected to the host computer for communication therewith via a communication line conforming to the SCSI standard, via a SAN, or via a LAN. 
   Further, an alternative configuration may be used so that the transmission of the area management data from the host computer to the storage controller is performed via a communication path other than a communication path for connecting the storage controller and the host computer. The use of such an alternative configuration will enable, for instance, communication load distribution. 
   EMBODIMENTS 
     FIG. 1  shows the configuration of a storage system according to an embodiment of the present invention. 
   For example, a storage controller  10  shown in this figure is a disk array device and a host computer  20  is a mainframe computer or a personal computer that uses the storage controller  10  as a storage resource. The storage controller  10  is connected to the host computer  20  via a communications means  40 . For example, the communications means  40  is a communication line conforming to the SCSI interface standard, a LAN (Local Area Network), or a SAN (Storage Area Network). 
   The storage controller  10  may include the following: a CPU  11  for controlling the various parts and functions in the storage controller  10  and executing and controlling various processing programs; a control memory  12  for storing various information; physical devices (not shown), such as disk drives, that serve as “storage devices”; a host interface  13 , which may serve as “means for receiving area management data” and/or “means for receiving a data input/output request”, for connecting to the host computer  20 ; a data controller  14  for controlling the data input/output to/from the physical device in accordance with a data input/output request received from the host computer  20 ; a cache memory  15 ; a data buffer  16  for temporarily storing the data to be registered in the cache memory  15 ; and a disk interface  17  for controlling the physical devices in accordance with the instructions from the data controller  14 . 
   The host interface  13  is equipped with one or more connection ports  131 . An external interface  26  of the host computer  20  is, for instance, a Host Bus Adapter that serves as a channel interface and may function as “means for transmitting area management data”. 
   In the storage controller  10 , one or more logical devices  18  are organized in physical storage regions provided by the physical devices. Each organized logical device is assigned a unique logical device ID that can be used when the host computer  20  designates a storage area of the storage controller  10 . In the present embodiment, it is assumed that five logical devices  18  are organized in the storage controller  10 , each of which being designated by logical device IDs are A, A′, B, C, and X. 
   An OS  21  runs on the host computer  20 . On the OS  21 , a logical volume management program  22 , application programs  23 , and an area management program  24  run. 
     FIG. 8  is a block diagram that shows the configuration of the host computer  20 . The host computer  20  comprises at least a CPU (Central Processing Unit)  201 , a memory  28 , a storage device  202 , and the above-mentioned external interface  26 . 
   The CPU  201  takes charge of the overall control of the host computer  20  and realizes various functions according to the present example by executing various programs stored in the memory  28 . The storage device  202  can store various programs and data. For example, hard disk devices and the like may be used for the storage device  202 . In the present example, the storage device  202  stores the OS  21 , the logical volume management program  22 , the application programs  23 , and the area management program  24 , details of which being explained later on. 
   The logical volume management program  22  organizes one or more logical volumes  27  in the logical storage regions of the logical devices  18  in the storage controller  10 , and provides storage areas specified by the logical volumes  27  to the application programs  23 . An example of the logical volume management program  22  may be a so-called SoftRAID program, which manages the storage areas provided by the logical devices of the storage controller  10  according to the RAID (Redundant Array of Independent Disks) method based on software and offers the resulting organized logical volumes  27  to the application programs  23 . The following description assumes that a SoftRAID program is used as the logical volume management program  22 . 
   For example, each application program  23  is a database software, which is provided with a scheme for organizing and managing the data to be stored in the storage controller  10  in accordance with a predefined specification, that is, a mechanism for verifying the suitability of the data. Each application program  23  is also provided with an algorithm for checking whether the data to be processed is organized in accordance with a predefined specification, that is, for verifying whether the data is suitable. 
   The area management program  24  manages an area management table  25  stored in a memory  28  of the host computer  20 . Details on the area management table  25  are explained below. The area management program  24  is capable of transmitting the area management table  25  to the storage controller  10  at an appropriate timing. This will be described in detail later. 
   =Area Management Table= 
     FIG. 2  shows an example of an area management table  25 . The area management table  25  is generated for each logical volume  27 , which is organized by the logical volume management program  22 . When, for instance, the relationship between the logical devices  18  and logical volumes  27  is changed by the logical volume management program  22 , the area management program  24  updates the area management table  25  as necessary in accordance with the information acquired from the logical volume management program  22 , the application programs  23  and the like. 
   In  FIG. 2 , a logical volume ID  210  is a unique identifier that is assigned to each logical volume  27 . The logical volume ID indicates which logical volume  27  the area management table  25  corresponds to. An OS control information offset  211  and OS control information size  212  indicate the storage location in a logical device  18  for storing OS control information that is given by the OS  21  to manage the logical devices  18  and logical volumes  27 . An example of the OS control information may be file control information. 
   A logical volume control information offset  213  and logical volume control information size  214  indicate the storage location in a logical device  18  for storing the logical volume control information that is generated by the logical volume management program  22  to manage the logical volumes  27 . The logical volume control information is the information used by the logical volume management program  22  to manage the logical devices  18 . An example of the logical volume control information may be stripe configuration information that is necessary when the logical volume management program  22  operates the logical devices  18  according to the RAID method. 
   A logical device ID  215  is an ID of a logical device  18  that composes a logical volume  27 , and an application ID  216  is an ID of an application program  23  that uses that logical volume  27 . A user, for instance, may register an application ID by operating the user interface of the host computer  20 . 
   An application handling data size  217  is the size of data handled when an application program  23 , which uses the logical volume  27 , performs a data input/output operation to a logical volume  27 . A stripe size  218  is the data size to be adopted when the logical volume management program  22  writes data on a logical device  18  by striping the data according to the RAID method. A whole data size  219  is the total storage capacity of the logical volume  27 . 
   =Area Management Table Transmission= 
   The area management table  25  is transmitted from the host computer  20  to the storage controller  10  by the area management program  24  at an appropriate timing. An “appropriate timing” for such transmission may be, for example, when the host computer  20  is started up or when the area management table  25  is updated, or at a time that has been set to a scheduling function of the area management program  24 . 
   Upon receipt of an area management table  25  from the host computer  20 , the storage controller  10  stores the table in a logical device  18 . In the present embodiment, although it is assumed that the area management table  25  is stored in a logical device  18  having a logical device ID “X”, the area management table  25  may instead be stored in the control memory  12  or the like. 
     FIG. 3  is a flowchart depicting processing steps that are followed when the host computer transmits an area management table  25  to the storage controller  10 . These processing steps can roughly be divided into two processes: a process in which the area management program  24  acquires an area management table  25  indicative of the latest position; and a process in which the program transmits the acquired area management table  25 . 
   First, the area management program  24  initializes the contents of flags and other items to be used during processing (S 310 ), requests the OS  21  to hand over the latest OS control information offset  211  and OS control information size  212 , and acquires such information (S 311 ). Next, the area management program  24  checks whether the area management table  25  exists in the memory  28  of the host computer  20  (S 312 ). 
   If the area management table  25  is not found in the memory  28 , the area management program  24  generates an area management table  25  in the memory  28  (S 313 ). If, on the other hand, the area management table  25  is found in the memory  28 , the area management program  24  compares the OS control information offset  211  and OS control information size  212  in the area management table  25  with the acquired OS control information offset  211  and OS control information size  212  (S 314 ). If the contents of the acquired information differ from those in the area management table  25 , the area management program  24  updates the table  25  to register the acquired information (S 315 ). After such an update, the area management program  24  turns ON an update flag (S 316 ). 
   Next, the area management program  24  acquires also the logical volume control information offset  213  and logical volume control information size  214  from the OS  21  and performs a comparison process similar to that for the OS control information. That is, the acquired information and the contents of the area management table  25  in the memory are compared (S 317 ,  318 ), and if the contents of the acquired information are found to be different from those in the area management table  25 , the area management program  24  updates the area management table  25  so as to reflect the acquired information (S 319 ), and turns ON the update flag after such an update (S 320 ). 
   According to the above-explained procedure, the area management table  25  representing the latest state is generated in the memory  28 . 
   Next, the area management program  24  checks the update flag (S 321 ). When the update flag is ON, the area management program  24  transmits the contents of the area management table  25  stored in the memory  28  to the storage controller  10  (S 322 ). Upon receipt of the area management table  25 , the storage controller  10  stores the table in logical device X. 
   The above-described process for transmitting the area management table  25  from the host computer  20  to the storage controller  10  is performed as necessary, for instance, at the time of starting up the OS  21  in the case where there has been a change in the OS control information or logical volume control information or in the case where the configuration of logical volumes  27  has been changed, for example, if there has been a change in the number of logical devices  18  that compose the logical volumes  27 . This ensures that the area management table  25  indicative of the latest status will always be set in the storage controller  10 . 
   =Logical Device Management Table= 
   In the control memory  12  of the storage controller  10  is stored a logical device management table  121 . An example of a logical device management table is shown in  FIG. 4 . In relation to a logical device ID  411 , this table manages, for example, the following: a LUN (Logical Unit Number)  412 , which is unique to each logical device ID  411 ; a storage capacity  413  of each logical device  18 ; and a port ID  414 , which is the ID of a port  131  of the host interface  13  to which each logical device  18  is connected. The contents of the logical device management table  121  are maintained up-to-date. For example, they are manually updated by an operator with a management terminal (not shown) connected to the storage controller  10  or automatically updated according to, for example, the information stored in the storage controller  10  or transmitted from the host computer  20 . 
   =Data Status= 
   Next, it will be explained how the data output from an application program  23  running on the host computer  20  is stored in a logical device  18  of the storage controller  10 , paying attention to data configuration. 
     FIG. 5A  illustrates a data unit that is used when an application program  23  performs a data input/output operation to a logical volume  27 . The data size of the data unit  51  is equal to the handling data size of the application program shown in  FIG. 2 . 
     FIG. 5B  shows how the logical volume management program  22  divides a data unit  51 , which is shown in  FIG. 5A , when performing an input/output operation to the storage controller  10 . In the example shown in this figure, the data unit  51  is divided into three sections: data  52 , data  53 , and data  54 . 
     FIG. 5C  shows how data  52 , data  53 , and data  54  are stored in the logical devices  18 . This figure shows an example where a logical volume  27  having a logical volume ID  210  of “001h”, which is designated by an application program  23 , is formed by a logical device  18  having a logical device  3 D  215  of “A” and a logical device  18  having a logical device  3 D  215  of “A′”. The divided data  52  and  53  are stored in the logical device  18  having the logical device ID  215  of “A”; the divided data  54  is stored in the logical device  18  having the logical device  3 D  215  of “A′”. 
   The fixed areas of these logical devices  18  store the aforementioned OS control information  55 ,  56  and logical volume control information  57 ,  58 . 
     FIG. 6A  illustrates a data unit, as shown in  FIG. 5A , in a data format complying with the SCSI standard.  FIG. 6B  illustrates the data presented in  FIG. 5B  in a SCSI data format. 
   As illustrated in  FIG. 6B , to each of the opcode fields  611  to  613  in a command frame, a command indicating the type of process requested is set. In the examples in this figure, a write command is set. To each of the LUN fields  621  to  623 , the logical device  3 D  215  or LUN (logical Unit Number) to be the target of process is set. In the examples, “0001h” is set in LUN fields  621  and  622  and “0002h” is set in LUN field  623 . To logical address fields  631  to  633  are set the addresses corresponding to the storage-start location (i.e., a location at which storage is to start) in a logical device  18  onto which data  52  to  54  are to be written. To data length fields  641  to  643  are set the data lengths corresponding to the write data  52  to  54  in the respective command frames. 
   The above description deals with a case where a data write request is output from an application program  23 . When a data read request is output, a read command will be set to each of the above-mentioned opcode fields  611  to  613 , the addresses for designating the data read start location (i.e., a location at which reading of data is to be started) in a logical device  18  will be set to the logical address fields  631  to  633 , and the size of the data to be read will be set to each of the data length fields. 
   =Data Verification Process= 
   The data verification process, which is performed by the storage controller  10  when the host computer  20  transmits SCSI data to the storage controller  10 , will now be explained. 
   The data verification process is performed by executing a data verification program  122  (algorithm) that the storage controller  10  stores in its control memory  12 . This program thus may serve as “means for verification”. The data verification program  122  is prepared for each application program  23  that runs on the host computer  20 . The data verification program  122  comprises a function for verifying, before performing processing of target data (i.e., data to be processed), whether the target data complies with a predefined specification, the function performing processing equivalent or superior to the aforementioned algorithm that the application program  23  running on the host computer  20  comprises. 
   The data verification program  122  is stored in the control memory  12 , for instance, through transmission from the host computer  20  or manual operation of an operator working with a management terminal (not shown) for the storage controller  10 . To each data verification program  122  to be stored is assigned an ID of the associated application program  23 . 
   The data verification process is for checking whether or not the target data conforms to a predefined specification required by an application program  23 . For this reason, among the entire data that has been stored in the storage region of a logical device  18 , only the area for storing the data that is input from or output to the application program  23  has to be subjected to the data verification process. Therefore, prior to the data verification process, a process for excluding such an area is performed, as described later. 
   Next, explanation will be made of the data verification process performed in the storage controller  10  using the flowchart shown in  FIG. 7 , taking a case in which a data write request for writing data  51  shown in  FIG. 6A  is transmitted from an application program  23  running on the host computer  20  and a write command frame shown in  FIG. 6B , which corresponds to the data write request, is transmitted to the storage controller  10 . This process is performed, for instance, by a microprogram stored in the control memory  12  of the storage controller  10 . 
   Upon receipt of a command frame carrying a write command from the host computer  20  (S 711 ), the storage controller  10  stores the command frame in a data buffer  16  (S 712 ). The storage controller  10  then refers to an area management table  25  stored in a logical device  18  having a logical device ID of “X” to acquire the OS control information offset  211 , the OS control information size  212 , the logical volume control information offset  213 , and the logical volume control information size  214  for the logical device ID that is set in the received data write request (S 713 ). Further, the storage controller  10  refers to a logical device management table  121  to acquire the storage capacity  413  of the logical device  18  corresponding to the above-mentioned logical device ID (S 714 ). 
   Next, the storage controller  10  stores the addresses (e.g., at least one start address and end address) for designating, among the whole storage region of the logical device  18  corresponding to the above-mentioned logical device ID, an area or areas except for the areas designated by the above-mentioned OS control information offset  211 , the OS control information size  212 , the logical volume control information offset  213 , and the logical volume control information size  214  (S 715 ). The storage area having been designated by the above addresses is hereinafter referred to as the candidate area for verification. 
   Next, the storage controller  10  compares the above-mentioned candidate area for verification designated by the addresses with the address that is set in the logical address field  631  to  633  of the received command frame (S 716 ). If the address that is set in the logical address field is not in the candidate area for verification, the data verification process is ended (S 717 ). If, on the other hand, the address is contained in the candidate area for verification, the storage controller  10  further checks whether the whole storage area, which is defined by the address set in the logical address field and the data length set in the data length field  641  to  643  of the received command frame and designated to be the write destination into which the write data is to be written, falls in the candidate area for verification (S 718 ). 
   If the whole designated storage area is in the candidate area for verification, the storage controller  10  sets the whole storage area, which has been designated as the write destination, as the target area for data verification, and then stores the addresses for defining such an area (e.g., the start and end addresses defining the area) (S 719 ). 
   If, on the other hand, the whole storage area is not in the candidate area for verification, the storage controller  10  sets the area starting from the above-mentioned logical address contained in the command frame up to the end address of the candidate area for verification as the target area for data verification, and stores the addresses for defining such an area (e.g., the start and end addresses defining the area) (S 720 ). 
   After the target area for data verification is set as described above, the storage controller  10  obtains the application program ID that is associated with the logical device  18  to be written. It should be noted that the storage controller  10  stores the correspondence indicative of a relation between application IDs and data verification programs  122  provided for each of the application programs  23 . Therefore, the storage controller  10  starts the data verification program  122  that is associated with the obtained application program ID (S 721 ). 
   Upon starting the data verification program  122 , the storage controller  10  gives the above-mentioned addresses, which designate the target area for data verification, to the data verification program  122 . The data verification program  122  then starts to perform a data verification process in relation to the storage area of the logical device  18  that is designated by the above-mentioned addresses (S 722 ). 
   If an error is detected during the data verification process performed by the data verification program  122  (S 723 ), the storage controller  10  transmits a message indicative of such error (e.g., a message indicating an illegal request or write error) to the host computer  20  (S 724 ). If no error is detected, the storage controller  10  transmits the write data in the command frame, which is presently stored in the data buffer  16 , to the cache memory  15 , and writes the data onto the logical device  18  (S 725 ). 
   The above description deals with a case where the storage controller  10  receives a data write request from the host computer  20 . However, when a data read request is received, instead of verifying the data in the command frame, data to be read is read out from a storage device, stored in the data buffer  16 , and verified by performing the same process as that for the write command. That is, even when a data read request has been received, the data verification process will be performed and, if any error is detected, the associated error message will be sent to the host computer  20 . Accordingly, for example, an application program  23  can be notified of data unsuitability (i.e., that the “suitability” of the data is not assured) before the read data is handed over to the application program  23 . It is therefore possible to prevent any data loss and damages in data, and also prevent the application program  23  from performing erratic operations. 
   As described above, according to the present invention, the storage controller  10  can also acquire information necessary for data verification. Therefore, the data verification process which is usually performed by an application program  23  can also be performed by the storage controller  10 . Since the storage controller  10  also verifies the data suitability demanded by an application program  23 , it becomes possible to further enhance data management accuracy. 
   =Others= 
   It should be noted that in the foregoing description, the logical volume management program  22  is not necessarily an essential structural component. 
   Further, the entire contents of the area management table  25  does not always have to be transmitted from the host computer  20  to the storage controller  10 ; it may be configured so that only differential data indicative of differences occurring due to changes in data is transmitted. 
   When the area management program  24  is to be executed for the first time, nothing is written in the area management table  25  of the host computer  20 . In such an instance, it may be configured so that the area management table  25  is transmitted to the storage controller  10  on the assumption that, for instance, some changes have been applied to the area management table  25 . 
   Further, by connecting the host computer  20  to the storage controller  10  with a LAN or like network to transmit the area management table  25  via the LAN, the area management table transmission from the host computer  20  to the storage controller  10  can also be performed with high speed. 
   Although the preferred embodiment of the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from spirit and scope of the inventions as defined by the appended claims.