Storage system and method for controlling the same

A storage system comprising:

• a controller;
• a cabinet for accommodating a plurality of rewritable removable media;
• at least two drives for performing read and write operations on said removable media;
• and
• a transporter for transporting said removable media between said cabinet and said drives;
• wherein, in response to a write request from a host computer, said controller causes said transporter to transport a first removable medium to which to write data from said cabinet to a first drive;
• wherein, every time a data write operation is performed on said first removable medium, said controller updates update count management information by which to manage an update count for each of said removable media;
• wherein, when the update count for said first removable medium is found to have exceeded a predetermined threshold value, said controller causes said transporter to transport a spare second removable medium from said cabinet to a second drive;
• and
• wherein said controller copies data held on said first removable medium to said second removable medium before causing said controller to transport said second removable medium to said cabinet for storage therein in place of said first removable medium.

A controlling method for use with a storage system having a plurality of rewritable removable media, comprising the steps of:

• managing an update count for each removable medium being used;
• if said update count is found to exceed a predetermined threshold value for a first removable medium, copying contents of said first removable medium to a second removable medium;
• and
• using said second removable medium in place of said first removable medium after the copying.

A storage system comprising:

• a cabinet for accommodating a plurality of rewritable removable media;
• a drive for performing read and write operations on said removable media;
• a transporter for transporting said removable media between said cabinet and said drive;
• and
• a controller for controlling said drive and said transporter;
• wherein, in response to a request from a host computer, said controller causes said transporter to transport a first removable medium from said cabinet to said drive whereby data are written to storage regions of said first removable medium;
• wherein, if data cannot be written to said storage regions, the data to be written to said first removable medium are written to previously furnished spare regions so that said spare regions are used in place of said storage regions;
• and
• wherein, if the number of said spare regions in said first removable medium is found to be less than a predetermined value, the data held on said first removable medium are copied to a previously furnished second removable medium.