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Optimizing a Large Optical Library by a Genetic Algorithm

IP.com Disclosure Number: IPCOM000113844D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 166K

Publishing Venue

IBM

Related People

Dimitri, KE: AUTHOR [+4]

Abstract

If a library is being designed around magazines holding a plurality of removable optical media, the following questions arise: o When is it better to give magazines positional priority in the library stack. o When is it better to leave one slot in the magazine empty for performance and when is it better to fill that slot with a disk for capacity. o When is it better to empty inactive disks to a magazine versus keeping the disk mounted in the inactive devices. o When is it better to remove inactive magazines from devices versus keeping the magazines stationed at the devices.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 29% of the total text.

Optimizing a Large Optical Library by a Genetic Algorithm

      If a library is being designed around magazines holding a
plurality of removable optical media, the following questions arise:
  o  When is it better to give magazines positional priority in
     the library stack.
  o  When is it better to leave one slot in the magazine
     empty for performance and when is it better to fill that
     slot with a disk for capacity.
  o  When is it better to empty inactive disks to a magazine
     versus keeping the disk mounted in the inactive devices.
  o  When is it better to remove inactive magazines from devices
     versus keeping the magazines stationed at the devices.

      A genetic analysis is proposed to determine the tradeoff
between performance and capacity in the multidisk magazine in an
optical library.  This genetic analysis begins with the following
definition of four binary "genes:"
  o  Magazine Positional Priority (Gene #1)

          0 means that there is no positional priority in the storage
    slots.

          1 means that a positional priority for storage is invoked.
    Hot magazines are stored closest to the devices and cold
    magazines are stored the furthest away.
  o  Floating Home Magazine for the Disk (Gene #2)

          0 means that the disk has a fixed home magazine and that
    this magazine is kept full of disks.

          1 means that the disk can float in the subset of magazines
    with this attribute.  One slot is kept open in these magazines to
    allow disk swapping at the device.
  o   Inactive Disk Attribute (Gene #3)

          0 means that the disk from this magazine is a candidate for
    being preemptively unloaded when it is inactive in a device.

          1 means keep the inactive disk at the drive until a mount
    request comes.
  o   Inactive Magazine Attribute (Gene #4)

          0 means that this magazine is a candidate for being
    preemptively moved when it is inactive at a device.

          1 means keep the inactive magazine at the drive until a
    mount request comes.

These 4 genes are organized into the following 16 (2 to the 4th
power) strings of "DNA," the Table.  Each binary string is a digital
representation of a magazine algorithm.

          16 Strings of DNA for each Magazine in the Library
  String    Positional    Floating Home    Inactive     Inactive
  #         Priority      Magazine for     Disk         Magazine
                          Disk             Attribute    Attribute
   0        0             0                0            0
   1        1             0                0            0
   2        0             1  ...