Patent ID: 6463513
Filing Date: 2002-10-08
Classification: G06F,Y10S

Abstract:
A method for increasing the availability of cache storage for storing redundant copies of identifiable data volumes in one of a plurality of data storage libraries, said data storage libraries each having cache storage and backing storage, said identifiable data volumes each directly associated with an updatable synchronization token, said synchronization token indicating the relative update levels of said directly associated redundant copies, said data storage libraries coupled to a plurality of directors, each said data storage library migrating data volumes from said cache storage to said backing storage in a predetermined sequence, said method comprising the steps of:said data storage library maintaining said synchronization token directly associated with said data volume; in response to a selection of said data storage library as a primary data storage library for redundant identifiable data volumes having identically updated said directly associated synchronization tokens, said data storage library placing said data volume in said cache storage at a low priority of said predetermined sequence; and in response to a selection of said data storage library as a secondary data storage library for redundant identifiable data volumes having identically updated said directly associated synchronization tokens, said data storage library placing said data volume in said cache storage at a high priority of said predetermined sequence for migrating said data volume to said backing store on said high priority basis of said predetermined sequence, said migration freeing and making available a portion of said cache storage.