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Browse Prior Art Database

Exploitation of Mount Caching for an Automated Tape Library

IP.com Disclosure Number: IPCOM000109408D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 89K

Publishing Venue

IBM

Related People

Aden, EL: AUTHOR [+3]

Abstract

An automated tape library is a storage subsystem comprised of storage racks containing tape cartridges, tape transports through which tape data is accessed, and a library accessor that moves tape cartridges from racks to transports and back. Tape transports can have cartridge loading devices into which several tape cartridges can be pre-loaded, and from which cartridges can be mounted at demand, independent of library accessor activity.

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

Exploitation of Mount Caching for an Automated Tape Library

       An automated tape library is a storage subsystem
comprised of storage racks containing tape cartridges, tape
transports through which tape data is accessed, and a library
accessor that moves tape cartridges from racks to transports and
back.  Tape transports can have cartridge loading devices into which
several tape cartridges can be pre-loaded, and from which cartridges
can be mounted at demand, independent of library accessor activity.

      Customer tape mount requirements are seldom constant -- mount
demand varies considerably from hour to hour within a day, from day
to day within a month, and often from month to month within a year.
Analysis of customer data has shown that peak-hour demand rates are
typically two to three times average-hour rates.  Therefore, it is
not necessary to provide a constant high level of mount performance
to satisfy customer needs.  A lower level of sustained performance
with a peak-period "boost" would be sufficient.

      Such a peak-period boost can be achieved by utilizing tape
cartridge loading devices available for each tape transport.
Selected classes of cartridge (e.g., "scratch" and multi-volume data
sets) can be preloaded by the library accessor into these devices
during non-peak periods.  During peak periods, a mount request for
one of these classes of cartridge can be satisfied by cycling one of
the loading devices.  Apart from relieving the library accessor of a
significant portion of peak-period mount load, these devices provide
very fast mount time, since the cartridge is already at the tape
transport, and so does not have to be fetched from normal library
storage.  Further, since each loading device serves just one tape
transport, there is never a queuing delay for this type of mount.
All loading devices can be mounting tape cartridges at the same time,
thus providing a high degree of mount parallelism.

      The collection of cartridge loading devices constitutes a
"mount cache," much as high-speed memory serves as...