Tape drives generating best access order of randomly stored files on a tape

摘要

A tape drive adapted for providing a best access order for files or data sets on a tape loaded into the tape drive. The tape drive includes a processor and memory storing a file location table for the tape. The file location table includes identifiers for a plurality of files on the tape and location information for the plurality of files on the tape. The tape drive includes an order determination module, executed by the processor, processing an order request. The order request, from a host or user, includes a list of the files on the tape from which to generate, based on the location information in the file location table, a reordered list defining an order for accessing the files on the tape. The reordered list or best access order has (or produces via tape drive access) an access time for the files that is minimal or reduced.

主权项

1. A tape drive for providing best access order for data on a tape, comprising:
a processor; memory storing a file location table for a tape loaded into the tape drive, wherein the file location table includes identifiers for a plurality of files on the tape and location information for the plurality of files on the tape; and an order determination module, executed by the processor, processing an order request comprising a list including a number of the files on the tape to generate, based on the location information in the file location table, a reordered list defining an order for accessing the number of the files on the tape, wherein an access time for the number of the files for the reordered list is less than for an order of files on the list of the order request, wherein the order determination module includes a factorial routine that is performed when the number of the files is less than or equal to a threshold value, wherein the factorial routine generates a set of all possible orders for accessing the number of the files, wherein the order determination module further comprises a time determination routine processing each of the possible orders in the set of all possible orders to determine an access time for the number of the files and wherein the order determination module selects the reordered list as an order from the set of all possible orders with a shortest of the access times, and wherein the time determination routine determines the access times based on a distance between start of file locations for pairs of adjacent ones of the files in each of the possible orders and by adding time penalties when a next one of the files in the one of the possible orders is in a different wrap or in a different servo band on the tape.