Abstract: In a data storage subsystem, drive-level processing treats data storage media as WORM by automatically advancing a write append limiter as data is written, and preventing changes to data occurring before the write append limiter. Despite this media's WORM nature, the drive-level processing permits limited overwriting of data at the end of tape since the write append limiter lags the current write location by the margin of a write allowance index. Thus, despite the drive's treatment of the media as WORM, the drive permits overwriting of trailing metadata in order to facilitate write append operations.

Abstract: Optimizing the retrieval of blocks of data from a tape media of a longitudinal serpentine tape drive. A device block map (DBM) is retrieved from the tape media and stored in memory. The DBM comprises a table having one or more rows and one or more columns for each block of data stored on the tape media. The columns are selected from the group comprising a wrap column, a position column, a logical block column, and a file identifier column. One or more retrieval paths for requested blocks of data are determined from an image of the physical layout of the requested blocks on the tape media generated by linear interpolation of the DBM stored in memory. Each of the retrieval paths comprises an ordered sequence of the blocks of data and the manner in which the tape media is to be traversed to accomplish the retrieval of the ordered sequence. A sum of distances is determined for each of the retrieval paths and an optimal one of the retrieval paths is selected based on the determined sum of distances.

Abstract: In a data storage subsystem, drive-level processing treats data storage media as WORM by automatically advancing a write append limiter as data is written, and preventing changes to data occurring before the write append limiter. Despite this media's WORM nature, the drive-level processing permits limited overwriting of data at the end of tape since the write append limiter lags the current write location by the margin of a write allowance index. Thus, despite the drive's treatment of the media as WORM, the drive permits overwriting of trailing metadata in order to facilitate write append operations.

Abstract: A method, apparatus, and article of manufacture for optimizing the retrieval of blocks of data from a tape media of a longitudinal serpentine tape drive. A device block map (DBM) is retrieved from the tape media and stored in memory. The DBM comprises a table having one or more rows and one or more columns for each block of data stored on the tape media. The columns are selected from a group comprising a wrap column, a position column, a logical block number column, and a file identifier column, wherein the wrap column indicates a track where the block of data is recorded on the tape media, the position column indicates a physical position where the block of data is recorded on the tape media, the logical block number column indicates a logical block number for the block of data, and a file identifier column indicates a logical file identifier for the block of data.

Abstract: Storage shelves of a mass data storage library are organized into a plurality of subsets for the purpose of conducting an inventory of media stored in the shelves. In response to an inventory command, the inventory is conducted in a predetermined order by subset. Upon completion of the inventory of each subset, the completion is posted in a list. A command input detects newly issued commands (subsequent to the inventory command), and places them in a queue. After completion of the inventory of a subset, and upon detecting a command for a non-inventory process (such as a media move), the inventory is interrupted and stopped. The move is conducted, and, upon completion of the move, the inventory is resumed. If a newly issued command is an inventory command, the inventory command is incorporated into the inventory process.

Abstract: A method, embodiable in computer readable program code, and a SCSI multiport device allow multiple hosts to be coupled to associated device ports of the multiport device. Using standard SCSI signaling, any host port may reserve the multiport device at its one associated device port. In response to a Reservation command, the multiport device is reserved in accordance with standard SCSI protocol. The method implements, at all the device ports other than the one device port, OFFLINE or status signaling which indicates that the multiport device is unavailable or offline. In response to a Device Reset from the one host port, the method operates the multiport device in accordance with standard SCSI protocol, including resetting the reservation of the multiport device, and additionally maintains the implemented OFFLINE or status signaling.

Abstract: Various data storage formats help to efficiently locate, read, and write user data stored on magnetic tape media. A tape is formatted by writing multiple segment-headers, free from any interleaved access of user data Adjacent segment-headers are spaced by a predetermined interval to define multiple data storage segments. Segment-headers all contain a unique key, which is copied into a key index to identify valid segments. After formatting, normal tape accesses can be performed. Without erasing any old headers or data, a new formatting scheme can be established by writing new segment-headers on the tape. The new segment-headers include a new unique key, replacing the previous key in the key index. Previous segment-headers stored on the tape are ignored, since they lack the updated key. Segments may be selectively grouped to provide independently addressable partitions. Mapping between segments and partitions can use a fixed relationship (e.g.

Abstract: Various data storage formats help to efficiently locate, read, and write user data stored on magnetic tape media. A tape is formatted by writing multiple segment-headers, free from any interleaved access of user data. Adjacent segment-headers are spaced by a predetermined interval to define multiple data storage segments. Segment-headers all contain a unique key, which is copied into a key index to identify valid segments. After formatting, normal tape accesses can be performed. Without erasing any old headers or data, a new formatting scheme can be established by writing new segment-headers on the tape. The new segment-headers include a new unique key, replacing the previous key in the key index. Previous segment-headers stored on the tape are ignored, since they lack the updated key. Segments may be selectively grouped to provide independently addressable partitions. Mapping between segments and partitions can use a fixed relationship (e.g.