Method and system for transferring duplicate files in hierarchical storag management system

Abstract

In order to provide HSM that can effectively use the storage capacity of an upper Tier in an HSM system, a lower Tier of the HSM system detects a group of files having the same data content from a plurality of files stored in the lower Tier, and keeps at least one of the real data of the group of files having the same data content while deleting the rest of the data. The upper Tier receives the process result from the lower Tier. Then, in response to a read request from the host computer that specifies a file included in the group of files and transferred to the upper Tier from the lower Tier, the upper Tier identifies the at least one of the data that is kept and corresponding to the specified file, and responds to the host computer.

1 . A computer system comprising:
 a first computer; and   a second computer,   wherein: the first computer includes a first storage area for storing files transmitted/received to/from a host computer;   the second computer includes a second storage area for storing files migrated from the first computer;   the first computer migrates a first file stored in the first storage area, to the second computer, according to the access state from the host computer;   the second computer generates duplicate file information by determining whether the migrated first file and any other files are identical to each other, and transmits the generated duplicate file information to the first computer; and   when receiving a read request to the first file from the host computer, the first computer determines whether a second file identical to the first file is stored in the first storage area based on the received duplicate file information, and when determining that the second file is stored in the first storage area, the first computer responds to the host computer by using the second file.   
     
     
         2 . The computer system according to  claim 1 ,
 wherein: when migrating the first and second files stored in the first storage area to the second computer according to the access state from the host computer, the first computer provides first and second file identifiers corresponding to the first and second files, respectively;   the second computer receives the migrated first and second files, and generates the duplicate file information indicating that the first and second files are identical to each other;   when receiving a read request to the second file from the host computer, the first computer transmits an instruction asking the second computer to transfer the second file from the second computer;   the second computer transmits the second file and the duplicate file information to the first computer;   the first computer stores the received second file as a file corresponding to the second file identifier into the first storage area, and transmits the second file to the host computer;   the first computer manages the first file identifier associated with the second file identifier, based on the duplicate file information; and   when receiving a read request to the first file from the host computer, the first computer determines that the second file identical to the first file is stored in the first storage area, based on the duplicate file information and on the first and second file identifiers.   
     
     
         3 . The computer system according to  claim 2 ,
 wherein the duplicate file information includes the first and second file identifiers, and an identifier corresponding to a group including the first and second files.   
     
     
         4 . The computer system according to  claim 2 ,
 wherein the duplicate file information includes the first and second file identifiers, and an identifier corresponding to the data of the first and second files.   
     
     
         5 . The computer system according to  claim 1 ,
 wherein, when determining that the second file identical to the first file is stored in the first storage area based on the duplicate file information, the first computer prevents an instruction from asking the second computer to transfer the first file from the second computer.   
     
     
         6 . The computer system according to  claim 1 ,
 wherein, when determining that the second file identical to the first file is not stored in the first storage area based on the duplicate file information, the first computer transmits an instruction asking the second computer to transfer the first file from the second computer, and transmits the first file received from the second computer to the host computer.   
     
     
         7 . The computer system according to  claim 1 ,
 wherein, when determining that the second file identical to the first file is stored in the storage area based on the duplicate file information, the first computer retrieves the data of the second file to restore the first file, and transmits the restored first file to the host computer.   
     
     
         8 . The computer system according to  claim 1 ,
 wherein the second computer transmits the duplicate file information to the first computer at a predetermined timing.   
     
     
         9 . The computer system according to  claim 1 ,
 wherein, in response to request from the first computer, the second computer transmits the duplicate file information to the first computer.   
     
     
         10 . The computer system according to  claim 1 ,
 wherein a first physical storage medium constituting the first storage area has a higher access performance than that of a second physical storage medium constituting the second storage area.   
     
     
         11 . The computer system according to  claim 2 , further comprising a management computer connected to the first and second computers,
 wherein: with respect to the files that the host computer has requested to access, the first computer manages the capacity of the second file as the capacity information of the file that the first computer received from the second computer and used to respond to the host computer, and manages the capacity of the first file as the capacity information of the file that the first computer stored in the first storage area and used to respond to the host computer without receiving from the second computer; and   the first computer transmits to the management computer the capacity information of the file transferred to the first computer from the second computer, as well as the capacity information of the file that the first computer stored in the first storage area and used to respond to the host computer without receiving from the second computer.   
     
     
         12 . A file controller connected to a host computer and another file controller, and further connected to a storage device constituting a storage area for storing files transmitted/received to/from the host computer,
 the file controller comprising:
 a processor for controlling access requests to the storage area from the host computer; and 
 a memory for storing a program executed by the processor, 
   wherein the processor performs the steps of:
 migrating a first file stored in the storage area to the other file controller according to the access state from the host computer; 
 receiving the de-duplicate file information generated by the other file server to determine whether the migrated first file and the other files are identical to each other; and 
 when receiving a read request to the first file from the host computer, determining whether the second file identical to the first file is stored in the storage area based on the received duplicate file information, and when determining that the second file is stored in the storage area, responding to the host computer by using the second file. 
   
     
     
         13 . The file controller according to  claim 12 ,
 wherein the processor further performs the steps of:
 when migrating the first and second files stored in the storage area to the second computer according to the access state from the host computer, providing first and second file identifiers corresponding to the first and second files, respectively, and storing the management information in the memory; 
 when the duplicate file information is generated in the other file controller with respect to the migrated first and second files to indicate that the first and second files are identical to each other; 
 when receiving a read request to the second file from the host computer, transmitting an instruction asking the other file controller to transfer the second file from the other file controller; 
 receiving the second file and the duplicate file information from the other file controller; 
 storing the received second file as the file corresponding to the second file identifier into the storage area, and transmitting the second file to the host computer; 
 updating the management information associated with the first file identifier stored in the memory with the second file identifier; and 
 when receiving a read request to the first file from the host computer, determining that the second file identical to the first file is stored in the storage area based on the duplicate file information and on the first and second file identifiers. 
   
     
     
         14 . The file controller according to  claim 13 ,
 wherein the duplicate file information includes the first and second file identifiers, as well as an identifier corresponding to the data of the first and second files.   
     
     
         15 . The file controller according to  claim 12 ,
 wherein, when determining that the second file identical to the first file is stored in the storage area based on the duplicate file information, the processor prevents an instruction from asking the other file controller to transfer the first file from the other file controller.   
     
     
         16 . The file controller according to  claim 12 ,
 wherein, when determining that the second file identical to the first file is not stored in the storage area based on the duplicate file information, the processor transmits to the other file controller an instruction asking it to transfer the first file from the other file controller, and transmits the first file received from the other file controller to the host computer.   
     
     
         17 . The file controller according to  claim 12 ,
 wherein, when determining that the second file identical to the first file is stored in the storage area based on the duplicate file information, the processor retrieves the data of the second file to restore the first file, and transmits the restored first file to the host computer.   
     
     
         18 . The file controller according to  claim 12 ,
 wherein a first physical storage medium constituting the storage area has a higher access performance than that of a second physical storage medium constituting the storage area connected to the other file controller.   
     
     
         19 . The file controller according to  claim 13 ,
 wherein: the file server is connected to a management computer;   with respect to the files that the host computer has requested to access, the processor manages the capacity of the second file as the capacity information of the file that the processor received from the other file controller and used to respond to the host computer, and manages the capacity of the first file as the capacity information of the file that the processor stored in the storage area and used to respond to the host computer without receiving from the other file controller; and   the processor transmits to the management computer the capacity information of the file transferred from the other file controller, as well as the capacity information of the file that the processor stored in the first storage and used to respond to the host computer without receiving from the other file controller.   
     
     
         20 . A computer readable recording medium that records a program executed by a file server connected to a host computer and another file server, the recording medium comprising the steps of:
 controlling access requests from the host computer, and storing files transmitted/received to/from the host computer into a storage device connected to the file server;   migrating a first file stored in the storage area to the other file server according to the access state from the host computer;   receiving the duplicate file information generated by the other file server by determining whether the migrated first file and the other files are identical to each other; and   when receiving a read request to the first file from the host computer, determining whether a second file identical to the first file is stored in the storage area, and when determining that the second file is stored in the storage area, responding to the host computer by using the second file.