Systems and methods for data migration in a clustered file system

Abstract

Systems and methods for providing more efficient handling of I/O requests for clustered file system data subject to data migration or the like. For instance, exemplary systems can more quickly determine if certain files on primary storage represent actual file data or stub data for recalling file data from secondary storage. Certain embodiments utilize a driver cache on each cluster node to maintain a record of recently accessed files that represent regular files (as opposed to stubs). A dual-locking process, using both strict locking and relaxed locking, maintains consistency between driver caches on different nodes and the data of the underlying clustered file system, while providing improved access to the data by the different nodes. Moreover, a signaling process can be used, such as with zero-length files, for alerting drivers on different nodes that data migration is to be performed and/or that the driver caches should be flushed.

1 . 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 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, 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   when the request for the read-only lock on the signal file is granted to 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.