Abstract: System and method for performing optimized restores of a multi-class file system. More actively accessed data may be assigned to higher storage classes and less actively accessed data may be assigned to lower storage classes in the multi-class file system. In a restore, the higher storage class(es) including more actively accessed data may be restored first. The multi-class file system may then be brought online for access by application(s). The lower storage class(es) may then be restored. In one embodiment, if a request for data that have not been restored is received, the file system may obtain an estimated time until restore of the requested data from the restore mechanism. The file system may then notify the application of the estimated time until restore. The application may notify a user of the estimated time, and may generate another request for the data after the estimated time has elapsed.

Abstract: System and method for providing immutable data containers in tiered storage hierarchies. Embodiments may allow fulfillment of regulatory requirements for retaining certain data through management of a user-defined policy. The policy may specify what data in the file system needs to be stored as immutable data to the immutable data container in the file system. File system data may be tracked, and data specified by the policy may be transparently and automatically stored to the immutable data container within the file system. Updates to the data specified by the policy may also be stored to the immutable data container. This may be performed without overwriting or modifying the earlier version(s) of the data stored to the immutable data container, and thus every version of the data specified by the policy may be stored to and, if necessary, reconstructed from the immutable data container.

Abstract: System and method for performing operations in a multi-class file system without requiring split mirrors. For one or more storage classes in the multi-class file system, operations that require stable copies of the storage classes may be performed without using split mirrors. In one embodiment, read-only data may be assigned and/or migrated to lower storage classes, and operations may be performed on the read-only storage classes without using split mirrors. In one embodiment, to perform an operation without using a split mirror, a write lock of a storage class may be examined to determine if the write-locked storage class has been written to during the operation on the storage class and, if so, the operation may be retried for the storage class. In one embodiment, the file system software may be blocked from enabling a storage class for writing for the duration of the operation on the storage class.

Abstract: System and method for implementing a file system across different storage classes in a storage system. Embodiments may define multiple classes of storage and automatically and transparently migrate data in the storage classes within the same file system to meet the usage needs of the business. Embodiments may transparently adapt the cost of storage to the usage patterns of data on the storage, thereby reducing the amount that customers need to spend for their storage. In embodiments, storage devices may be classified into different classes of storage to implement a multi-class file system. Embodiments may provide a multi-class storage mechanism for managing and implementing user-defined policies for assigning and migrating data within the multi-class file system. The multi-class storage mechanism may determine where to initially place data, and may transparently migrate data to other storage classes according to the policies. Migrated data remains online within the file system.

Abstract: System and method for performing backups of a multi-class file system are described. In one embodiment, more recently modified data may be assigned and/or migrated to higher storage classes and less recently modified data may be migrated at time intervals to lower storage classes in the multi-class file system. Backups of each of the storage classes may be performed at time intervals. In one embodiment, the backups may be image-based backups of the storage devices in the storage classes. In one embodiment, the lower storage classes may include one or more read-only storage classes including less-recently modified data that are backed up less frequently than higher storage classes including more-recently modified data. In one embodiment, files migrated to lower storage class(es) may be compressed.

Abstract: Provided is a method, system, and program for automatically handling an error when retrieving a file for an application. An error is detected while the application retrieves a file from the storage device. A user defined policy is checked to determine whether a backup copy should be restored, and the file is restored from the backup copy if the user defined policy indicates that the backup copy should be used.