Abstract: A system and method is disclosed for maintaining, in a Storage Area Network (SAN), the consistency of a local copy of a remote file system sub-tree obtained from a remote source. Directory structure of the remote file system sub-tree is mapped to a remote container attached to the SAN and each remote object of the remote file system sub-tree is represented as a local object component of the remote container. Next, each of the local objects are labeled with attributes associated with the represented remote object, and metadata describing each of the local objects is stored in a metadata server. Also, a consistency policy is associated with each of the local objects in the remote container (wherein the policy defines conditions for checking freshness of said labeled attributes), and the local object components of remote container is updated in accordance with the consistency policy.

Abstract: Addressed is a system and method for remote data caching and replication by local copy maintenance of remote data within a SAN file system. Distributed Storage Tank (DST), an extension to a SAN file system, provides for transparent SAN client access of local copies by importing, exporting, and storing data using network file access protocols as well as by providing assurance of metadata and file content validity. A Remote Access Agent (RAA) handles protocol implementation and conversion necessary for communication with remote data sources. Controlled by a consistency policy, consistency is maintained by RAA fetching and updating local copies if modifications have occurred to a file since it was first stored as a local copy in local storage. Additionally, RAA returns metadata pertaining to the requested data. A SAN client obtains metadata corresponding to the requested data and utilizes it to directly access locally stored copies of remote data.

Abstract: A system and method are provided that is used by software implemented Redundancy Array of Inexpensive Disk (RAID) arrays to achieve adequate performance and reliability, as well as to improve performance or low cost hardware Raids. The enhancements to the basic RAID implementation speeds up recovery time for software RAIDS. A method is provided for storing data in an array of storage devices. A plurality of block locations on the storage devices are logically arranged as a parity group wherein a parity block stored in a block location as part of a parity group is logically derived from the combination of data blocks stored in the parity group, and each block in a parity group is stored on a different storage device. A plurality of parity groups are grouped into a parity group set. A request is received to write a new data block location on a storage device. The old data block stored at the block location is read. The new data block is written to the block location.