Abstract: Tokens corresponding to data units written to a rewritable file system are stored, where an ordering relationship is maintained among the tokens, where the ordering relationship is such that a first token corresponding to a first data unit is of a lesser numerical value in comparison to a second token corresponding to a second data unit, and where the first data unit is written at an earlier point in time in comparison to the second data unit. The rewritable file system is reverted to an indicated point in time based on the ordering relationship that is maintained among the stored tokens.

Abstract: A plurality of tokens corresponding to a plurality of data units written to a rewritable file system is stored, wherein an ordering relationship is maintained among the plurality of tokens, wherein the ordering relationship is such that a first token corresponding to a first data unit is of a lesser numerical value in comparison to a second token corresponding to a second data unit, and wherein the first data unit is written at an earlier point in time in comparison to the second data unit. The rewritable file system is reverted to an indicated point in time based on the ordering relationship that is maintained among the stored plurality of tokens.

Abstract: A method and system for managing a multi-volume data set request in an automated storage library. The library includes automatic means for prioritizing and selecting the optimum peripheral data storage device (PDSD) for mounting a data volume belonging to the requested multi-volume data set. The optimum PDSD is that one PDSD having the closest proximity to all volumes of a multi-volume data set. The automatic means include means for determining the location of each data volume in the requested multi-volume set and means for comparing the location of each volume to the location of peripheral data storage devices. The library system employs a weighted score based on the proximity of each PDSD to each volume in a multi-volume data set to prioritize and select the optimum PDSD when a multi-volume data set is requested. Each PDSD subsystem may include one or more PDSDs.

Abstract: In an data storage system, a volume transform filter is employed in conjunction with a RAID array manager to maintain logical volumes entirely on corresponding physical data storage volumes while maintaining parity information on a dedicated parity storage volume. This is achieved by modifying data access commands received from a host such that forwarding the modified commands to the RAID array manager in effect "tricks" the RAID array manager into maintaining the logical volumes without striping. This system provides data allocation with standalone data and parity storage volumes, which are easily exportable for convenient use in data storage libraries.