Switch device, system, backup method and computer program

A file access service system comprising:

• at least one terminal;
• a plurality of file devices, each including a file system;
• and
• an intermediate device logically arranged between said terminal and said plurality of file devices, said intermediate device furnishing said terminal which a file access service which allows said terminal to access said plurality of file systems as a single file system, termed hereinafter a ‘pseudo file system’;
• said intermediate device including means for commanding each of said plurality of file devices to start the generation of a snapshot which is a fixed image at a certain point in time of said file system of each of said plurality of file devices;
• each of said plurality of file devices generating a snapshot responsive to said command from said intermediate device for starting to generate the snapshot;
• said intermediate device also including means for setting a link across a plurality of said snapshots so that a plurality of said snapshots generated respectively by said plurality of file devices correspond to said pseudo file system at the time of generation of said snapshots.

A method for taking a backup in a file access service system comprising

• at least one terminal;
• a plurality of file devices, each including a file system;
• and
• an intermediate device logically arranged between said terminal and said file devices;
• said intermediate device providing file access services which virtually render said plural file services accessible as a single file system, termed a ‘pseudo file system’, when viewed from said terminal;
• said method comprising the steps of
• said intermediate device distributing a command for starting to generate a snapshot which is a fixed image of a file system at a certain point in time, to a plurality of said file devices;
• said plural file devices receiving a command for starting to take snapshots from said intermediate device to formulate respective snapshots;
• and
• said intermediate device setting a link across a plurality of said snapshots so that said snapshots generated by said file devices are in correspondence with said pseudo-file system at the time of generation of said snapshots.

A switch device logically arranged between at least one client and a plurality of file servers, each provided with a file system, for providing file access services which virtually render said plural file systems accessible as a single file system, termed a ‘pseudo file system’, when viewed from said client;

• said switch device comprising:
• a unit that distributes a command for starting to generate a snapshot, which is a fixed image of a file system at a certain point in time, to a plurality of said file servers;
• and
• a unit that sets a link across a plurality of said snapshots so that said snapshots generated by said file servers on receipt of a command for starting to generate the snapshots so that said snapshots corresponds with said pseudo-file system at the time of generation of said snapshots.