Abstract:
To solve a problem of waste of management resources/wasteful management involved in the setting of information defining access rights of multiple users to a single file and the setting of differing file attributes information for each file, this system has a file attributes DB operating as a database managing file attributes, a accounting information DB as a database managing accounting information and a local file system storing file data. The accounting information DB holds records for each combination of a user or group and a server and adds records for each additional user or server.

Description:
BACKGROUND OF THE INVENTION 
   This invention concerns a system realized by using a plurality of network connected computers. 
   In recent years the volume of data provided by computers providing a service over a network and the number of users using these computers via a network has increased substantially in line with the increased diffusion throughout society of networks such as the Internet. 
   However, with conventional concentrated type computer systems in which a single computer manages all data required by a user the processing capabilities of the computers are limited and it is not possible to exceed those performance limits and provide all users with the data they require. The storage capacity of the storage devices connected to such computers is limited, moreover if there is computer failure it is not possible to access data. 
   This invention discloses technology for a dispersed type of computer system that solves these problems. 
   The technology disclosed in Document 1 “OceanStore, an Architecture for Global-Scale Persistent Storage,” John Kubiatowicz et al., appearing in Chapter 2 of Proceedings of the Ninth International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS 2000), November 2000 provides for placement and replication of data in each of a plurality of storage devices and servers installed in geographically dispersed locations (hereinafter referred to as “sites”). This allows the load for data processing and the data itself to be dispersed through a plurality of servers. Further, if any of these servers fails the data can be reconstructed using replicated data in other servers. 
   Hereinafter, any conglomeration of data like a program for example used by a user or a computer is referred to as a “file.” 
   Conventional concentrated management computer systems and the server infrastructure environment with servers dispersed on a global scale as disclosed in Document 1 allow a plurality of users to access files managed by computers. In order to ensure security under such an environment access rights to files must be set for each user of the system. Moreover, in order to accommodate the various uses demanded by the many users, it may be necessary to set file attributes as conditions dictate in response to such uses for each individual file in such a computer system. 
   With conventional programs (hereinafter “file systems”) managing files run by a computer, the types and number of file attributes that can be set for a file are limited. Further, as file attributes are managed and fixed for the entire file system it is not possible to increase or decrease the number and types of file attributes applicable to each individual file at will, so there is a lack of flexibility in file attributes management. 
   Moreover, when there are storage service providers performing services for storage and replication of files in storage devices managed by computers existing at a plurality of sites, different conditions for charges (hereinafter “accounting policy”) may be applied by providers for different storage devices managed by computers at each of those sites, thereby creating a demand to acquire information necessary for accounting (hereinafter “accounting information”) based on the relevant accounting policy. The only file attributes information that can be acquired with existing file systems is static information such as file capacity or the number of file accesses, while specific accounting information based on the accounting policy of a site, information on for example the type of storage device housing a file, cannot be collected. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a computer system in which there is flexibility to add or delete file attributes. 
   A further object of the present invention is to provide a computer system that acquires accounting information reflecting the different accounting policies of a plurality of sites. 
   In order to achieve the above objectives the computer system according to the present invention comprises 
   a first computer for managing a storage device holding data for managing files (hereinafter “file management information”) stored in the computer system and 
   a second computer connected to the first computer via a network, for managing a storage device holding the actual data of files (hereinafter “file data”). 
   In this computer system the first computer receives a file access request from a user and searches file management information that it manages based on the content of the file access request, then, in accordance with the content of the information thus searched, this first computer transmits to the second computer via the network, a file processing request coordinated in response to the file access request. Upon receiving this file processing request, the second computer performs the processes specified by that file processing request and transmits the result to the first computer. Upon receiving this result the first computer transmits a result to the user based on the content of the result it received. 
   This file management information may include information on file attributes, as well as information on whether or not a file can be used and information showing file storage devices of the system. 
   Further, information on file attributes may include a table managing only files containing one of various file attributes. Here, one such conceivable attribute could be whether or not a file is encrypted but others are conceivable. 
   Moreover, this file management information may include accounting information, basically, information concerning usage of a file of each second computer by a user using the file. Here, as the first computer receives a file access request from the user, it updates information concerning file usage of each second computer in response to the content of the access. 
   Additionally, this computer system may have a computer for accounting management which uses accounting information in respect of each second computer and calculates charges for the user of a file. 
   There may be a plurality of first computers and second computers or the number of first computers may be just the number of sets of file management information stored in storage devices. 
   Moreover, there may be a plurality of second computers and replications of file data may be stored, dispersed through this plurality of second computers. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an example of the overall configuration of a computer system according to the present invention. 
       FIG. 2  shows an example of the different kinds of tables of a file attributes DB. 
       FIG. 3  shows an example of a accounting information DB. 
       FIGS. 4A , B and C show examples of file I/O request commands. 
       FIGS. 5A , B and C show examples of local file I/O requests. 
       FIG. 6  shows an example of a accounting information DB update request. 
       FIG. 7  is a flowchart showing the processes of MSVR  100 A. 
       FIG. 8  is a flowchart showing the processes of FSVR  300 . 
       FIG. 9  is a flowchart showing the processes of MSVR  100 B. 
       FIG. 10  is a flowchart showing the processes performed when creating a new file. 
       FIG. 11  shows examples of an ACL table searching request and registration request, an extended attributes table registration request and a location table searching request and registration request. 
       FIG. 12  shows examples of a accounting information table update request and registration request and registration and searching requests for the different kinds of tables used for the processes for calculating an amount for invoice. 
       FIG. 13  is a flowchart showing the processes of accounting server  900 . 
       FIGS. 14A , B and C show respectively a user table, accounting information table and accounting policy table. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Embodiments of the present invention will now be described with reference to the drawings. 
     FIG. 1  shows an embodiment of a computer system according to the present invention. This computer system comprises site  1500 A and site  1500 B, with connectivity between these sites via Internet  1000 . 
   Site  1500  comprises a plurality of computers (hereinafter “clients”)  800 , used by users, a plurality of computers (hereinafter “CN”)  101  for managing file management information (hereinafter “metadata”), a plurality of computers (hereinafter “SN”)  301  for managing file data and a plurality of storage devices  600 . Here, mutual interconnectivity between clients  800 , CN  101  and SN  301  is provided via network  700 . Mutual interconnectivity between the plurality of storage devices  600 , CN  101  and SN  301  is provided via storage network  500  constructed of fiber cables or the like. 
   SCSI or Fibre Channel protocol is used as a transmission protocol for storage network  500 . 
   Network  700  is connected to network  700  of site  1500 B via Internet  1000 . Accordingly, each client  800 , CN  101  and SN  301  of site  1  can transmit through SN  301 C and network  700  of site  1500 B and Internet  1000 . 
   Client  800 , CN  101  and SN  301  are computers comprising a processor, memory, parts for performing input and output, a network interface and storage device. 
   The processor of CN  101  runs a server program that performs management of metadata (hereinafter “MSVR”) and a server program that performs management of the database storing metadata (hereinafter “DBMS”). These programs are stored in memory. The processor of SN  301  runs a server program that performs management of file data (hereinafter “FSVR”)  300 . FSVR  300  is stored in memory of SN  301 . 
   A storage device  600  comprises a control part and a storage part. An electromagnetic disk, semiconductor disk or optical disk may be used as a storage medium of the storage part. Further, a storage device  600  may include for its storage part a disk device that uses one of such disks or a storage device system such as a disk array using a plurality of disk devices. 
   CN  101  and SN  301  run respectively MSVR  100  and FSVR  300  and cooperate to perform management of files stored in storage device  600 . According to this embodiment metadata such as file attributes and accounting information for example and file data are respectively managed through different computers and different storage devices  600 . This allows flexible management of file attributes. 
   In the storage part of storage device  600 A are stored file attributes database (hereinafter “DB”)  110  and accounting information DB  210  for accounting information on each user. In the file attributes DB 110  are stored file attributes table  120 , ACL table  130 , extended attributes table  140 , location table  150  and file ID bitmap  160 . In accounting information DB  210  is stored server by server accounting information table  220 . 
   CN  101 A runs MSVR  100 A and manages file attributes corresponding to file data stored in storage device  600 B and  600 C using file attributes DB 110 . CN  101  A runs MSVR  100 B and uses DB  210  for managing information for calculating accounting applied to a user when the user uses a file stored in the computer system. 
   A local file system (hereinafter “local FS”)  310  is stored in storage devices  600 B and C. Local FS  310  comprises file data  320 , metadata  330  for managing file data and a program for managing said metadata  300  and said file data. Information showing the data volume and storage locations in storage device  600  of file data  320  managed by local FS  310  is stored in metadata  330 . 
   SN  301  runs FSVR  300 , to control and manage local FS  310 . Local FS  310 A is managed by SN  301 A, local FS  310 B is managed by SN  301 B, local FS  310 C is managed by SN  301 C and local FS  310 D is managed by SN  301 D. 
   The computer system according to this embodiment operates such that when a client  800  creates a file a plurality of files with the same contents are automatically created at CN  101 . File data of each of that plurality of files is transmitted to different SN  301  and then stored in the respective local FS  310  managed by those SN  301 . File data stored in each of these local FS  310  is hereinafter referred to as local files. 
   According to this embodiment, a plurality of such local files exists for each file. The storage location for each of these local files is decided by CN  101  and the information showing this storage location is registered in location table  150  in file attributes DB 110  in accordance with instructions from CN  101 . CN  101 A runs MSVR  100 A to manage basic file attributes such as file size and creation date in file attributes table  120 . 
   Moreover, CN  101 A runs MSVR  100 A to manage access rights to files for each client  800  through ACL table  130 . Again, CN  101 A runs MSVR  100 A to manage other file attributes through extended file attributes table  140 . 
   CN  101 B runs MSVR  100 B and uses accounting information DB  210  to manage information necessary for accounting a user using files. 
   Generally, because characteristics such as performance and reliability of each storage device  600  managed by SN  301  differ, the accounting policy applied to users may differ for each SN  301  or storage device  600 . Accordingly, CN  101 B creates a accounting information record for each pair of a user and SN  301  managing the storage device  600 , and by registering the records in server by server accounting information table  220 , collects accounting information for each SN  301  and/or each site. 
   According to this embodiment CN  101  manages accounting information and file attributes using a relational type database. 
     FIG. 2  shows an example of the composition of the tables of file attributes DB  110 . File attributes shared by all files are stored in file attributes table  120 . File attributes table  120  comprises the entries FILE-ID  2210  in which a file identifier is registered, OWNER  2220  in which is stored the ID of the file owner, DATE  2230  in which a file&#39;s creation date is stored, SIZE  224  that stores information on file size and TYPE  2250  that stores information showing file type. There is one record for each file in file attributes table  120 . 
   Information concerning access rights restrictions applied to each user for a file is stored in ACL table  130 . Basically, ACL table  130  is comprised of each of the entries FILE-ID  2110  in which is registered a file&#39;s identifier, USR  2120  in which a user&#39; identifier is registered, READ  2130  and WRITE  2140  in which is registered information on whether read access right and write access right to a file exist or not and EXPIRE  2150  in which is registered information on the expiration of a time period in which it is possible to access a file. Records corresponding to the combination of a file and a user exist in ACL table  130  for the number of file-user combinations that exist. 
   Extended attributes table  140  is used as an attributes table for managing attributes corresponding to a file&#39;s type.  FIG. 2  shows an example of extended attributes table  140  used as an attributes table for managing encryption file attribute. Here, extended attributes table  140  comprises the entries of FILE-ID  2410  in which is registered a file&#39;s identifier and encryption KEY  2420  in which is registered encryption key information. 
   Here, if the file managed by this computer system is an encrypted file the extended attributes table  140  shown in  FIG. 2  is used (the encrypted file is registered in that table) but if the file is of another type, this extended file attributes table  140  is not used (the file is not registered in that table). In this way, files of specific types can be managed through specific tables as an extended attributes table  140  storing file attributes is established individually for each file attribute. Management in this way enables management of a variety of different file attributes without an excessive increase in the size of a table. 
   Information showing the storage location of file data is held in location table  150 . Location table  150  comprises the entries of FILE-ID  2310  in which a file&#39;s identifier is registered and location  2320  in which is registered the location of stored file data. 
   The entry FILE-ID is included in all of the above-mentioned tables, file attributes table  120 , ACL table  130 , extended attributes table  140  and location table  150 . Accordingly, each table has a structure of a relational database providing mutual interaction between them using the entry of the FILE-ID, enabling necessary file attributes to be searched as required. 
     FIG. 3  shows an example of the composition of server by server accounting information table  220  which comprises each of the entries USR  3110  in which a user&#39;s identifier is registered, FSVR-ID  3120  in which is registered an identifier of an FSVR  300  run by SN  301 , usage volume  3130  in which is registered the total volume of files stored in a storage device  600  managed by SN  301  executing FSVR  300 , Total No. of Files  3140  in which is registered the number of files stored in a storage device  600  as well as Rsize  3150  in which is registered the volume of data read by a user from storage device  600  and Wsize  3160  in which is registered the volume of data written-in by a user to storage device  600 . 
   Because server by server accounting information table  220  accumulates information on usage by a user of local FS for each SN  301  (basically, FSVR  300  run by SN  301 ), it has records for each user-SN  301  pair. 
   CN  101 B runs MSVR  100 B, and by searching the contents of accounting information DB  210  using information registered in USR  3110  as the key, is able to acquire information on the conditions of usage of each user of storage devices  600  managed by each SN  301 . 
   The description of this embodiment has used an example wherein file attributes DB  110  and accounting information DB  210  are managed using relational databases however it is also suitable to use object oriented databases or XML databases. 
   The processes involved according to the present invention when a user reads-out a file or updates a file (writes data to a file) will now be described. 
   Updating of a file by a user according to this invention will now be described. For the purposes of this explanation it is assumed that a file, “FILE  1 ” has already been created in this computer system. When a user (given USR  1  for an identifier) that uses client  800 A performs an update of data in FILE  1 , first client  800 A runs AGENT  810  and transmits a file update request (hereinafter “WRITE request”)  4100  to CN  101 A. 
   The top layer of  FIG. 4  shows a basic example of a write request transmitted from client  800 A to CN  101 A. Write request  4100  includes entries of command type  4110 , user identifier  4120 , file identifier  4130 , write commence offset  4140 , data size  4150  and data  4160 . 
   Basically, the following information is registered in the respective entries of the write request according to this embodiment. In the entry command type  4110  is shown “WRITE” indicating that this request is a data update request, in the entry user identifier  4120  is “USR  1 ” information showing the user issuing the request, and in the entry file identifier  4130  is registered the information “FILE  1 ” specifying the file that is the subject of the operation. 
   In the entries write commence offset  4140 , data size  4150  and data  4160  is stored respectively, the location inside the file of the data to be updated, the data size and the actual data itself. 
     FIG. 7  is a flowchart showing the processes of CN  101 A after receiving a write request  4100 . CN  101 A executes these processes by running MSVR  100 A. 
   Upon receiving write request  4100 , in order to confirm access rights of the user, CN  101 A creates a search request to search ACL table  130  stored inside storage device  600 A using the received FILE  1  file identifier and USR  1  user identifier as the key. CN  101 A commences running DBMS  102 A in order to run this search request produced. 
     FIG. 11  shows the contents of ACL table search request  600 A that provides a basic example of a search request. 
   ACL table search request  6000  comprises the entries of command name  6001 , select field name  6002 , searching subject table name  6003  and reference conditions  6004 . In the example of  FIG. 11 , command name  6001 A specifies “SELECT”, select field name  6002 A specifies “WRITE”, searching subject table name  6003 A specifies “ACL TABLE” and searching conditions  6004 A are “FILE-ID=FILE 1  AND OWNER=USR  1  AND CURDATE( )&lt;EXPIRE”. 
   Basically, the above described registered contents specify that a record for which the registered file-ID is FILE  1 , the owner field is USR  1  and the expire field has a period for which the value is greater than the current date must be searched from ACL table  130 . 
   By running DBMS  102 A, CN  101 A specifies that the searching processes instructed in ACL table search request  6000  be performed in file attributes DB 110  and receives the results from storage device  600 A. Here, high-speed database searching technology is used in the searching processes executed by CN  101 A running DBMS  102 A. For example, high-speed searching processes can be performed using a method like that described in U.S. Pat No. 6,353,820B1. 
   According to this embodiment the record that fulfills searching conditions  6004  of ACL table searching request  6000  is record  2111  so as a result of the searching operation the value registered in WRITE field  2140  of record  2111  is transmitted to CN  101 A (step  5000 ). 
   Thereafter CN 101 A decides whether or not the WRITE request is authorized or not based on whether or not the value of WRITE field  2140  thus transmitted is 1. According to this embodiment, when that value is 1 it shows that access is authorized to the file. Accordingly, as the value in the extracted WRITE field  2140  is 1, CN  101 A decides that this write request is authorized (step  5020 ). 
   When the value of WRITE field  2140  is 0, CN  101 A decides the write request is not authorized, notifies this non-authorization to the client  800 A and terminates procedures (step  5100 ). 
   When the write request is authorized, CN  101 A must next ascertain the location of the file to be updated. To do this, CN  101 A creates a location table search request  6100  and by running DBMS.  102 A to reference location table  150 , acquires location information including information that shows the location of the file for updating from storage device  600 A. 
     FIG. 11  shows an example of a location table search request  6100 . In this location table search request  6100  for acquiring the storage location of FILE  1 , the information “SELECT” is registered in search command  6101 , “LOCATION” is registered in acquire field  6102 , “location table” is registered in searching subject table  6103  and the information “FILE-ID=FILE  1 ” is registered in searching conditions  6104 . 
   Using this location table search request  6100 , CN  101 A running DBMS  102 A, specifies searching of location table  150  to storage device  600 , and acquires from storage device  600 A information concerning records  2311  and  2312  that have “FILE  1 ” specified in the file-ID field. 
   Thereafter, CN  101 A extracts the information “FSVR  1 :/FILE  1 ” and FSVR  3 :/FILE  1 ” stored in location field  2320  from these records (step  5030 ,  5040 ). 
   The CN  101 A having acquired the values stored in location field  2320  transmits a local file write request to all SN  301  included in those values. 
   The top layer of  FIG. 5  shows a basic example of a local file write request  4500 . This local file write request  4500  includes the entries transmission destination FSVR  4510 , local file I/O command  4520 , local file name  4530 , offset  4540 , size  4550  and data  4560 . 
   According to this embodiment, information indicating SN  301 A and C is registered in transmission destination FSVR  4510 . In local file I/O command  4520 , WRITE, showing that it is a local file update request is registered. In each of the other entries, the respective information showing the location of a local file (step  5050 ) is registered. 
     FIG. 8  is a flowchart showing the processes of SN  301 A (and  301 C) after receiving local file write request  4500 . Upon receiving local file write request  4500 , SN  301 A first refers metadata  350 A stored in storage device  600 B and acquires the size (hereinafter “used disk size”) in storage device  600  used for the local file  4530  specified in the local file write request received. As described, in addition to the size of data and the location of a local file stored in local file FS  310 A, metadata  330 A includes information on used disk size (step  5200 ). 
   Next, SN  301 A checks to ascertain that there is sufficient vacant space just to write-in the data received to local file system  310 A and if there is insufficient space, SN  301 A proceeds to step  5230  and an error is returned to CN  101 A (step  5205 ). 
   Next, SN  301 A performs the write-in WRITE processes of the received data into cache memory of SN  301 A having just the size specified by size  4550 , from the location shown in the information registered in OFFSET  4540  of the local file write request received, and performs SYNC processes to reflect in storage device  600 B, the result of those WRITE processes (step  5210 ). 
   After completion of the SYNC processes SN  301 A refers to metadata  330 A and acquires the used disk size for the local file after completion of the write-in. Thereafter SN  301 A compares the used disk size of storage device  600  before and after the local file write-in and calculates the storage space newly given to the local file through that local file write-in operation, in other words, calculating the newly allocated disk size (step  5220 ). 
   This newly allocated disk size is used when updating server by server accounting information table  220 . The volume in storage device  600  used by a user must be accurately reflected in the usage volume  3130  field existing in server by server accounting information table  220 . 
   Accordingly, although it is essential to ascertain storage volume newly allocated to cater for the WRITE processes to each local file, when there is an over write operation to a local file, processes to newly allocate storage space are not performed because the local file is already in existence, therefore the increase in used disk space cannot be ascertained. That is why the used disk size for a local file the subject of a WRITE operation both before and after the local file WRITE processes is compared and the newly allocated disk size calculated. 
   Finally SN  301 A transmits the results of the local file WRITE processes to CN  101 A. The content of that transmission to CN  101 A includes information on status showing whether or not the data update in line with the local file WRITE processes was successful or not, information showing the size of the completed write-in operation (the size of data the subject of the completed write processes) and information showing the newly allocated disk size newly allocated for the size of the completed write-in (step  5230 ). 
   This description will now be continued returning for reference back to  FIG. 7 . 
   Upon receiving the results of the write-in from SN  301 A (or  301 C) (step  5060 ) CN  101 A checks the information on status included in the result thus received (step  5070 ). 
   If there is an SN  301  that has a failed write-in operation, CN  101 A sends a request to that SN  301  to read all data of the local file concerned stored in storage devices  600  managed by that SN  301 . After obtaining that data from the SN  301 , CN  101 A transmits the data thus acquired to SN  301  that had a successful write-in operation and instructs those SN  301  to do a rewrite of the local file concerned in the storage devices  600  managed by those SN  301 . By doing this, CN  101 A returns all local files in the computer system back to the condition day were in prior to the write-in operation. Thereafter CN  101 A transmits a result showing an error to client  800 A (step  5075 ). 
   If the data write-in operation is successful for all local files/replications of the local file CN  101 A performs update processes in file attributes table  120 . Basically, this means CN  101 A updates the value of size field  2240  of the record corresponding to the file shown by file identifier  4130  inside file attributes table  120 , to reflect the size after execution of the WRITE operation. 
   Firstly, CN  101 A creates a size field acquisition request. This request includes for search command “SELECT”, file attributes table for search destination table, SIZE for acquire field and, for the searching conditions, information specifying conditions equivalent to those for file identifier  4130  as the file-ID field. By running DBMS  102 A and processing this SIZE field acquisition request, CN  101 A can acquire the value for SIZE field  2240  prior to execution of the WRITE operation. 
   Next, CN  101 A compares the value of the sum of the values registered for OFFSET  4140  and SIZE  4150  of WRITE request  4100  with the value registered in the size field  2240  acquired by the size field acquisition request. If the value acquired through the size field acquisition request is equivalent to or greater than the value of that sum, file size update processes are not necessary so CN  101 A finishes update operations for that file attributes table and proceeds to run the next process. 
   If the value acquired through the size field acquisition request is smaller than the value of that sum, CN  101 A updates the file attributes table with a new file size being the value of the sum of offset  4140  and size  4150 . 
   Basically, CN  101 A creates a file size update request. The file size update request includes for update command “UPDATE”, file attributes table for search destination table, “SET SIZE=new file size” for the update instruction and, for the conditions of the update, information specifying conditions equivalent to file identifier  4130  as the file-ID field. By CN  101 A running DBMS  102 A and processing this file size update request, the file attributes table is updated and the results are reflected in storage device  600  (step  5075 ). 
   When the file attributes table update processes are finished, CN  101 A transmits a accounting information DB update request  4700  to CN  101 B (step  5080 ). 
     FIG. 6  shows a basic example of the contents of an accounting information DB update request  4700 . This request has the entries transmission destination MSVR  4710 , user identifier USR  4720 , file server identifier  4730  and list  4740  of write information for each servers write-in to each server information list  4740 . 
   Write information list  4740  further includes the entries file server identifier  4750 , READ completion size  4760 , WRITE completion size  4770  and disk size  4780 . 
   Upon receiving the accounting information DB update request from CN  101 A, CN  101 B performs update processes in accounting information table  220  (step  5080 ). The update processes for accounting information table  220  will be described subsequently. 
   Receiving notice from CN  101 B that the accounting information DB update request has finished, CN  101 A reports to client  800 A that the write-in is complete (step  5090 ) and terminates the WRITE processes (step  5100 ). 
     FIG. 9  shows the procedures for the update processes in accounting information table  220  performed by CN  101 B upon receipt of the accounting information DB update request. 
   First, CN  101 B creates database update request  6200  instructing searching, with the pair of the user identifier and the identifier showing SN  301  as the key, of a record matching that pair inside accounting information table  210  and instructing that the information registered in the disk size  4780  and WRITE size  4770  entries included in the accounting information DB update request be added, respectively, to the usage volume  3130  and Wsize  3160  entries included in the a record thus searched, and commences running DBMS  102  B. 
   A database update command request has the entries command name  6201 , update table name  6202 , update information  6203  and searching conditions  6404 .  FIG. 12  shows a basic example of a database update request  6200 . The information shown in the entries for database update request  6200 A (and B) is “UPDATE” for command name  6201 A (and  6201 B), “accounting information table” for update table name  6202 A (and  6202 B) and “USR=USR 1  AND FSVR-ID=FSVR 300 A for searching conditions  6204 A (and  6204 B). Further, information showing “usagevolume=usagevolume+DSKsize” is specified in update information  6203 A and information showing “Wsize=Wsize+WCSIZE” is specified in update information  6203 B. 
   According to this embodiment the two records existing are record  3111  inside accounting information DB  210  selected by the key USR  1  and FSVR  1  and record  3112  selected by the key USR  1  and FSVR  3 . Thus, CN  101 B first creates database update command  6200 A (and  6200 B) in respect of record  3111  selected by the key USR  1  and FSVR  1  and runs DBMS  102 B (step  5400 ). 
   Based on that update command  6200 A (and  6200 B) as created, CN  101 B running DBMS  102  B performs write-in processes to storage device  600 A of the results of the sum of the newly allocated disk size and the size after the write-in is complete into the usage volume  3120  entry and Wsize  3150  entry of each record. 
   If at the time of the database update processes no record exists matching the combination of the specified user identifier and identifier specifying FSVR  300 , accounting information DB update processes produce an error. Then, CN  101 B collects from storage device  600 A, information (the results of the executed processes) showing whether or not the processes of database update request  6200  were successful. 
   CN  101 B refers to the results of the executed database update request colleted and decides whether the processes were successful (step  5410 ). 
   If the accounting information DB update processes based on the key of USR  1  and FSVR  1  fail, it means that a record matching that USR  1  and FSVR  1  key does not exist in accounting information table  220 . Accordingly, when an error occurs CN  101 B must transmit an add new record request to storage device  600 A. Such an error occurs when the write-in is for a new file but here, because it is an example of write-in-for an existing file, the error does not occur (step  5420 ). Details of these processes are described in the subsequent description of new file creation processes. 
   If the database update processes request in respect of USR  1  and FSVR  1  completes, CN  101 B decides whether or not the processes in respect of all the SN  301  specified in write-in to each file server information list  4740  of accounting information DB update request  4700  have been completed (step  5430 ). If those processes are not completed, the system reverts back to steps  5400  through  5420 . According to this embodiment, CN  101 B repeats steps  5400  through  5420  in respect of the next record with USR  1  and FSVR  3  as the key. 
   Once the accounting information update processes specified in write-in to each file server list  4740  included in the accounting information DB update request are complete for all SN  301 , CN  101 B transmits the results to CN  101 B thus completing the process (step  5440 ). 
   In this way the accounting information of each SN  301  can be easily managed through managing accounting information at the databases. 
   For this embodiment, the description used an example wherein file attributes DB 110  and accounting information DB  210  are managed by different CN  101  however a configuration in which both those DB are managed by one CN  101  is also suitable. 
   An example of file read, READ, processes by a user via client  800 A will now be described. Here, the explanation proceeds assuming that a file (hereinafter “FILE  2 ”) has already been created in the system. 
   When a user (hereinafter “USR  2 ”) using client  800 A performs a read of file  2 , client  800 A first runs AGENT  810  and transmits READ request  4200  to CN  101 A. 
   The middle layer in  FIG. 4  shows a basic example of a READ request. In the READ request  4200  are included each of the entries command type  4210 , user identifier  4220 , file identifier  4230 , read command offset  4240  and data size  4250 . In this example “READ” showing that this is a file read request is registered in the command type  4210  entry, “USR  2 ” is registered in the user identifier  4220  entry and information showing “FILE  2 ” is registered in the file identifier  4230  entry. In READ command offset  4240  and data size  4450  respectively is stored the location to which the data should be read in the file and the data size . 
   Unless otherwise required, CN  101 A performs the processes by running MSVR  100 A. 
   Upon receiving the READ request  4200 , in order to confirm access rights of the user, CN  101 A creates ACL table search request  6000 B to search ACL table  130  using the received FILE  2  file identifier and the USR  2  user identifier as the key. Next, CN  101 A runs DBMS  102 A, transmitting the above ACL table search request  6000 B to storage device  600 A and acquires information on the access rights from storage device  600 A. 
     FIG. 11  shows a basic example of ACL table search request  6000 B. In the respective entries of ACL table search request  6000 B is registered information that for command name  6001  B specifies “SELECT”, for select field name  6002 B specifies “READ”, for searching subject table name  6003 B specifies “ACL table” and for searching conditions  6004 B “FILE-ID=FILE 2  AND OWNER=USR 2  AND CURDATE( )&lt;EXPIRE”. 
   According to this ACL table search request  6000 B, CN  101 A runs DBMS  102 A and selects from the ACL table a record for which FILE-ID holds file  2 , OWNER field holds USR  2  and the expire field is a period greater than the current date, and acquires the READ field from storage device  600 A. 
   According to this embodiment, record  2113  is the record fulfilling the conditions registered in the entry for searching conditions  6004 B, so here, CN  101 A can acquire the value registered in the READ field  2130  of record  2113  from storage device  600 A area. 
   Thereafter, CN  101 A decides whether or not the READ request is authorized or not based on whether or not the value of the READ field obtained through running DBMS  102 A is 1. Here, the value of READ field  2130  is 1 so CN  101 A decides that this READ request is authorized. 
   When the value of READ field  2130  is 0, CN  101 A decides the READ request is not authorized, notifies this non-authorization to client  800 A and terminates procedures. 
   When the READ request is authorized, CN  101 A must ascertain the location of the file to be read. CN  101 A acquires information on the location, comprising the location of the file to be read from storage device  600 , by running DBMS  102 A just as in the case of the WRITE processes and processing the location table searching request  6100 . At this time “FILE-ID=FILE  2 ” is specified for searching conditions  6140  of location table searching request  6100 . 
   For this embodiment the location information obtained from these processes is the two items “FSVR  1 :/FILE  2 ” and “FSVR  3 :/FILE  2 ”. 
   Next, CN  101 A uses the file identifier FILE  2  to search file attributes table  120  and reads-out the record that satisfies the conditions from storage device  600 A. CN  101 A then acquires the information registered in the entries file size  2240  and file type  2250  of the selected record. According to this embodiment, CN  101 A acquires from selected record  2212  the information file size 20 MB and file type ENCRYPT. 
   Here, the information ENCRYPT means that the file is of a file type that must be encrypted before transmission when CN  101 A transmits a file on to client  800 . Accordingly, when transmitting the file on data to client  800 A, CN  101 A must encrypt the file data using the encryption key stored in extended attributes table  140 . 
   According to this embodiment, because the data can be acquired from any SN  301  managed storage device  600  where that file data is stored, CN  101 A can issue local file READ request  4600  to SN  101 A or SN  101 C or to both. 
   The following description provides an example where CN  101 A transmits a local file READ request to SN  301 A connected to the same network  700  as CN  101 A, however it would also be suitable for CN  101 A to issue to both SN  301 A and to SN  301 C a local file READ request to read one-half of the data out from each. 
   The middle layer in  FIG. 5  shows a basic example of a local file READ request  4600 . In this local file READ request  4600  are included the entries transmission destination FSVR  4610 , local file I/O command  4620 , local filename  4630 , OFFSET  4640  and SIZE  4650 . The information “READ” indicating a file read is registered in the entry local file I/O command  4620 . “FILE  2 ” indicating FILE  2  is registered in the entry local file name  4630 . 
   Unless otherwise required the processes of SN  301 A are performed by running FSVR  300 A. 
   Upon receiving local file read request  4600  SN  301 A performs local file READ processes to read data of the size specified in the entry SIZE  4550  from the location registered in the OFFSET  4640  entry of the specified local file. Basically, SN  301 A issues the read request to the appropriate storage device  600 B to acquire the required file data. 
   After finishing the local file READ processes SN  301 A transmits the data read and the size to CN  101 A. 
   Upon receiving the results of the local file READ request from SN  301 A, CN  101 A checks the status included in the result received to confirm whether or not the local file read operation was successful. 
   If the local file READ processes of SN  301 A fail, CN  101 A issues the same request to SN  301 C. In this way when a plurality of replications of a local file exist even if the read by a SN  301  fails it is possible for the read processes to be performed using another SN  301  thereby providing a more reliable system. If the read operations of all SN  301  registered in location table  150  fail CN  101 A returns an error to client  800 . 
   If the local file read from SN  301 A is successful CN  101 A creates a accounting information DB update request  4700  and transmits it to CN  101 B. Thereafter unless otherwise required CN  101 B performs processes by running MSVR  100 B. 
   CN  101 B having received accounting information DB update request  4700 , first creates accounting information table update request  6200 C instructing that storage device  600 A, using the pair of the user identifier and the identifier showing FSVR  300  as the key, searches a record matching that pair inside accounting information table  210  and adds in the information registered in the READ completion size  4760  entry included in accounting information DB table update request  6200 C to the Rsize  3140  entry included in the record thus searched. 
   Accounting information table update request  6200 C has the entries command name  6201 , update table name  6202 , update information  6203  and searching conditions  6204 .  FIG. 12  shows an example in which the registered information specifies “UPDATE” for command name  620 C 1 , “accounting information table” for update table name  6202 C, Rsize=Rsize+RCSIZE for update information  6203 C and “USR=USR 2  AND FSVR-ID=SN  301 A for searching conditions  6204 C. 
   In accounting information table  220  the record corresponding to the combination USR  2  and SN  301 A is record  3113 . 
   Accordingly CN  101 B runs DBMS  102  B and instructs storage device  600 A through accounting information table update request  6200 C, to perform write-in processes of the result to the Rsize  3140  entry of record  3113  of the result of the added up READ completion size entry. 
   Next, CN  101 B decides whether or not the processes have been completed for all file servers specified in write-in to each file server information list  4740  of accounting information DB update request  4700 , and if those processes are not completed the aforementioned database up date request processes are repeated. According to this embodiment, as there is no other specified file server, at this point CN  101 B terminates accounting information update processes and transmits the result to CN  101 A. 
   Upon receiving notification from CN  101 B that accounting information DB update request processes have completed, CN  101 A searches extended attributes table  140  inside storage device  600 A using the FILE  2  file identifier as the key to confirm that FILE  2  is registered in extended attributes table  140 . For the purposes of this example CN  101 A acquires from the KEY  2420  entry encryption KEY  1  required to transmit FILE  2  to client  800 . If the file is not registered in extended attributes table  140 , these processes for the attribute concerned (in terms of this example, the encryption) are not performed. 
   Thereafter, CN  101 A using KEY  1 , encrypts the read file data and transmits the encrypted file, the result of the read operation, to client  800 , completing the READ processes. 
     FIG. 10  shows the processes performed when a new file is created within this computer system. These processes are performed by CN  101 A running MSVR  100 A. 
   When a new file is created, the client  800  receiving instructions from a user runs AGENT program  810 A and transmits a create request  4300  to CN  101 A. The bottom layer in  FIG. 4  shows an example of a create request  4300 . Create request  4300  includes the entries file create command  4310 , user ID  4320 , file redundancy  4330 , file type  4340 , encryption key  4350  and usage term EXP_DATE  4360 . 
   Upon receiving create request  4300 , CN  101 A acquires a file ID allocated for the file. The file ID bitmap  160  is used for this process. In file ID bitmap  160  are registered file ID&#39;s that can be used by this computer system. Bit  1  is allocated for a file ID that is being used by the computer system and bit  0  is allocated to a file not being used. 
   CN  101 A refers file ID bitmap  160  stored in storage device  600 A and finds a 0 bit to enable it to acquire an unused file ID. When a 0 bit is found CN  101 A instructs storage device  600  to make that bit  1  to indicate that it is being used (step  5600 ). 
   Next CN  101  selects SN  301  storing the file data. File redundancy is specified in the create request  4300  and CN  101 A therefore selects the appropriate number of SN  301  for the specified level of redundancy. This selection utilizes a method wherein for example CN  101 A broadcasts messages over network  700  and selects in order from the first SN  301  returning a reply (step  5610 ). 
   Next, CN  101 A transmits local file create request  4690  to the SN  301  selected at step  5610  and receives the result of the execution of that request (step  5620 ). The bottom layer of  FIG. 5  shows an example of a local file create request  4690 . Local file create request  4690  has the entries FSVR  4691  of name of SN  301  creating the file, local file create command CREATE  4692  and local file name  4693 . Here, information showing the file ID selected at step  5600  is registered in local file name  4693 . 
   Upon receiving the local file create request  4690 , SN  301  runs FSVR and creates the local file using the value registered in the local file name  4693  entry specified in the command, before returning the result of the operation to CN  101 A. 
   Receiving this result, CN  101 A decides whether or not the received result for the local file create operation indicates success (step  5625 ). If the result is failure CN  101 A goes back to step  5610 . If the local file create operation is successful CN  101 A registers FSVR of the name of the SN  301  successfully creating the local file in location table  150 . This registration operation is performed through CN  101 A running DBMS  102 A. At this time to location registration request  6110  is instructed to storage device  600 . 
     FIG. 11  shows a basic example of a location registration request  6110 . Location registration request  6110  includes each of the entries, registration command INSERT  6111 , table name  6112  and values to register in record  6113 . In this example, for the values set for registration as values to register in record  6113 , the file ID allocated at step  5600  is set for the FILE-ID field and the “FSVR” of the name of CN  301  that successfully created the local file and the name of the created local file are set for the LOCATION field (step  5630 ). 
   After completing registration of information to location table  150 , CN  101 A finds out whether or not creation of the number of local files specified in file redundancy  4330  is complete (step  5640 ). If creation of that number of local files is not complete, the processes from step  5610  are performed again. 
   If creation of the specified number of local files is complete, CN  101 A finds out whether the file type specified at file type  4330  should be registered in extended attributes table  1140 , for the purposes of this example, finding out whether that file type is ENCRYPT or not (step  5650 ). 
   If the file type is ENCRYPT, CN  101 A performs processes to register in extended attributes table  140  the key specified in encryption key  4350  and the FILE-ID. These registration processes are performed by CN  101 A running DBMS  102 A at which time an extended attributes registration request  6020  is created and issued as an instruction to storage device  600 . 
     FIG. 11  shows an example of an extended attributes registration request  6020 . The extended attributes registration request  6020  includes each of the entries DB registration command  6021 , extended attributes table name  6022 , and values to register in record  6023 . For the values set for registration as values to register in record  6023 , the file ID allocated at step  5600  is set for the FILE-ID field and the key specified at encryption key  4350  for the KEY field (step  5660 ). 
   If CN  101 A determines at step  5650  that the file type is not ENCRYPT or after registration of the value in the extended attributes table at  5660 , CN  101 A performs registration processes in file attributes table  120 . 
   These registration processes in file attributes table  120  are performed by CN  101 A running DBMS  102 A however before that, CN  101 A creates the file attributes table registration request  6030  required when DBMS  102 A is run. 
     FIG. 11  shows an example of a file attributes table registration request  6030 . File attributes table registration request  6030  includes each of the entries DB registration command  6031 , file attributes table name  6032  and values to register in record  6033 . For the values to register in record  6033 , the ID allocated at step  5600  is set for the FILE-ID field, the value specified by user ID  4320  is set for the OWNER field, CURDATE( ) showing the current date is set for the DATE field, in the SIZE field is 0 and the value shown by the file type  4340  is set for the TYPE field. 
   CN  101 A refers to file attributes table registration request  6030  when running DBMS  102 A, performing registration processes in file attributes table  120  in accordance with the contents of that registration request, reflecting the result of that operation in storage device  600  (step  5670 ). 
   After completing the registration process in the file attributes table, CN  101 A performs registration processes in the ACL table for the new file.  101 A performs this registration process by running DBMS  102 A to process the following ACL table registration request  6010 . 
     FIG. 11  shows an example of an ACL table registration request  6010 . ACL table registration request  6010  includes each of the entries DB registration command  6011 , ACL table name  6012  and values to register in record  6013 . For the values set for registration as values to register in record  6013 , the file ID allocated at step  5600  is set for the FILE-ID field, the value specified by user ID  4320  is set for the OWNER field and the value EXP_DATE 4360  is set in the EXPIRE field (step  5680 ). 
   After completing registration processes to the ACL table, CN  101 A returns to client  800 , information indicating whether or not the file creation processes were successful. At this time, if those file creation processes were successful the file ID is returned to client  800  at the same time (step  5690 ). 
   Next an embodiment according to the present invention for calculating amounts to invoice to each user will be described with reference to  FIGS. 1 through 13 . As described above in this computer system information on usage of storage devices  600  is managed with respect to each SN  301 . Accordingly, even where the accounting policies and accounting rates of each SN  301  differ it is still possible to perform accounting processes reflecting those differences. 
   According to this embodiment, a new accounting server  900  and storage device  600 D storing a accounting data DB are added. Like client  800  described above, accounting server  900  is a computer. In storage device  600 D are stored all of the types of tables described hereafter. It is also suitable for accounting server  900  and storage device  600 D to be integrated in one body or to exist separately. According to this embodiment calculation of the amount to invoice each user is performed using accounting data DB  930 . 
   Basically, accounting server  900  runs accounting calculation program  910  to calculate the amount for invoice. Further, accounting server  900  manages a user ID of a user for performing accounting processes through a user table  940  and manages the accounting policy of each SN  301  using accounting policy table  950 . 
   Further, accounting server  900  searches accounting policy table  950  and user table  940  of storage device  600 D and runs DBMS  920 , a program for storing the result of the searching operations in accounting information table  960 . 
     FIG. 14  A shows an example of the configuration of user table  940 . This user table is a table holding information on users using this computer system and includes the entries user ID  7000 , name  7010 , invoice recipient  7020  and comments  7030 . 
   The top layer in  FIG. 14B  shows an example of accounting invoice table  960 . Accounting invoice table  960  is a table holding information concerning the amount for invoice for each constant period of usage, and based on the information in this table  960 , owners of this computer system invoice for usage charges. In this table  960  are included the entries usage month  7110  and invoice amount  7120 . It is also suitable in this table  960  to include entries registering information like whether or not the invoice has been issued and whether or not payment has been collected. 
     FIG. 14C  shows an example of accounting policy table  950  holding information on the accounting policies of each file server. Based on information stored in this table  950  and in accounting information DB  210 , accounting server  900  calculates the invoice amount for each user. This table  950  includes each of the entries file server name  7200 , volume unit price  7210  showing the monetary amount for usage in respect of each unit of volume, file unit price  7220  showing the monetary amount for usage in respect of each file, READ unit price  7230  showing the monetary amount for usage in respect of the unit size of each read and WRITE unit price  7240  showing the monetary amount for usage in respect of the unit size of each write-in. 
     FIG. 13  shows the processes performed by accounting server  900  running accounting calculation program  910 . 
   Accounting server  900  first acquires a user ID from user table  940  of storage device  600 D. This process is performed by accounting calculation server  900  running DBMS  920 , performing the following processes for user ID list acquisition request  6420 . 
     FIG. 12  shows an example of a user ID list acquisition request  6420 . For this user ID list acquisition request  6420  information showing “SELECT” is registered for search command entry  6421 , for acquisition field name entry  6422  “USR” is registered and “User Table” is registered for searching destination table name entry  6423  (step  5600 ). 
   Next accounting server  900  acquires the leading user ID of the acquired list (step  5610 ). 
   Thereafter, accounting server  900  performs accounting information acquisition processes based on the user ID acquired. These processes are realized by accounting server  900  issuing accounting information searching request  6410  to CN  101 B and CN  101 B running DBMS  102 B. 
     FIG. 12  shows an example of accounting information searching request  6410 . This accounting information searching request  6410  includes searching command “SELECT”  6411 , acquire all fields instruction “*”  6412 , searching destination table  6413  and searching conditions  6414 . The condition specified for searching conditions  6414  is acquisition of the equivalent record as for the user ID acquired at  5600  as the value for USR field  3110  (step  5620 ). 
   Accounting server  900 , having acquired the accounting information, next calculates the invoice amount in respect of each SN  301 . In the acquired accounting information is included records of server by server accounting information table  220  concerning all SN  301  used by the same user. Accounting server  900  uses the value of each FSVR-ID field  3110  included in each record to search accounting policy table  950 , acquires the accounting policy for each SN  301  then uses the accounting policies as acquired and the information of the records from server by server accounting information table  220  to calculate the amount for invoicing in respect of each SN  301 . 
   At this time the searching of accounting policy table  950  is performed by accounting server  900  running DBMS  920  and processing a accounting policy table searching request  6430 .  FIG. 12  shows the configuration of accounting policy table searching request  6430 . Accounting policy table searching request  6430  includes search command “SELECT”  6431 , acquire all fields instruction “*”  6432 , searching destination table “billing policy table”  6433  and searching conditions  6434 . The searching conditions  6434  specify the condition that FSVR field  7200  is equivalent to FSVR of the name of the SN  301  the subject of the present invoice amount calculation operation. 
   The invoice amount corresponding to the selected SN  301  can be calculated by adding to the values included in accounting information acquired at step  5620 , namely the values registered in usage volume field  3130 , No. of files field  3140 , Rsize field  3150  and Wsize field  3160 , the respective values of volume unit price  7210 , file unit price  7220 , READ unit price  7230  and WRITE unit price  7240  (step  5630 ). 
   Once the invoice amount for each SN  301  is calculated accounting server  900  totals the amount to be invoiced for all SN  301  and stores the result in accounting invoice table  960 . This process is performed by accounting server  900  running DBMS  920  and processing a accounting invoice table registration request  6400 . 
     FIG. 12  shows an example of a accounting invoice table registration request  6400 . This table includes search command “INSERT”  6401 , registration destination table name “accounting invoice table”  6402  and registration content  6403 . Registration content  6403  includes information showing user ID, usage month and invoice amount (step  5640 ). 
   Upon completing calculation of the invoice amount for SN  301 , accounting server  900  decides whether or not the processes for calculating the amount for invoice has been completed for all users. If there are any users in respect of which those processes are not completed accounting server  900  repeats processes from step  5610  through step  5640  (step  5650 ). 
   As described according to this embodiment of the present invention, it is possible to exercise detailed control over accounting operations that reflects the accounting policies of each SN  301 . 
   This invention realizes a computer system providing the flexibility to add file attributes for each file and allowing efficient management of access rights information for multiple users. Further, where a file is stored using a plurality of storage devices managed by servers dispersed in a plurality of sites, this invention realizes a computer system in which accounting information can be managed in respect of each site and each server. 
   It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.