Patent ID: 8209307

Claim:
A method for coordinating access to data in a storage management system, the method comprising: storing in a shared file system on a primary storage device a plurality of files comprising a first plurality of regular files not having been migrated to secondary storage and a plurality of stub files, the plurality of stub files being associated with a second plurality of regular files having been migrated to secondary storage; maintaining in a first driver cache of a first computer a first indication of first inodes associated with at least one of the first plurality of regular files on the primary storage device; maintaining in a second driver cache of a second computer a second indication of second inodes associated with at least one of the first plurality of regular files on the primary storage device; requesting with each of the first and second computers a read-only lock on a signal file on the shared file system to determine whether or not a migration operation is about to occur with respect to at least one of the first plurality of regular files on the primary storage device; when the request for the read-only lock on the signal file is denied of at least one of the first and second computers, where the denial indicates that a migration operation is about to occur and that the consistency of the first and/or second driver caches can no longer be trusted: clearing the respective first and/or second indications from the respective first and/or second driver caches of the at least one of the first and second computers; and operating in a first locking mode associated with requests to access the plurality of files, and when the request for the read-only lock on the signal file is granted to at least one of the first and second computers, where the grant indicates that a migration operation is not about to occur and that the consistency of the first and/or second driver caches can be trusted: preserving the respective first and/or second indications in the respective first and/or second driver caches of the at least one of the first and second computers; unlocking the signal file and re-requesting the read-only lock on the signal file after a predetermined period of time; and operating in a second locking mode associated with requests to access the plurality of files, the second locking mode less strict than the first locking mode.