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Browse Prior Art Database

Scratch Tape Drive Allocation Algorithm for Multiple Tape Libraries

IP.com Disclosure Number: IPCOM000106467D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 89K

Publishing Venue

IBM

Related People

Thrall, JL: AUTHOR [+2]

Abstract

A method is disclosed for allocating from several tape libraries a tape drive for a scratch mount that

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Scratch Tape Drive Allocation Algorithm for Multiple Tape Libraries

      A method is disclosed for allocating from several tape
libraries a tape drive for a scratch mount that

1.  enhances load balance between the several libraries, and
2.  maximizes drive availability for subsequent specific mounts.

      This method considers available drives as well as number of
scratch cartridges in allocating for a scratch mount a tape drive
from one of several tape libraries.  Selecting a drive from the
library with the greatest number of scratch cartridges would be used
until a threshold of available drives is reached.  Once a library
reaches this threshold, it would be excluded from primary
consideration for further scratch mounts until it rises above the
threshold.

      This method increases the probability that each library will
always have a drive available for a specific mount request.  Unlike
scratch mounts, a specific mount request can be satisfied only on a
drive located in the library in which the selected tape cartridge
resides.  This method also tends to balance workload over the
libraries by avoiding allocating scratch mounts to those libraries
whose available drives have fallen below the threshold, since drive
pool utilization will generally vary directly with workload
intensity.

      Consider the following scenario.  A user installation has two
automated tape libraries.  Currently library A has 500 scratch
cartridges and one available tape drive, while library B has 490
scratch cartridges and five available tape drives.  Considering only
number of scratch cartridges, the last remaining available drive in
library A would be selected for a scratch mount, even though library
B has ample free drives and just slightly fewer scratch cartridges.
This means library A will...