Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Volume Strategy Menu for Optical Disk Libraries

IP.com Disclosure Number: IPCOM000120300D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 115K

Publishing Venue

IBM

Related People

Monahan, C: AUTHOR [+3]

Abstract

Current implementation for storing data on optical disk drives is to fill one side of a cartridge, "flip" the cartridge, and then fill up the other side. This can lead to being "volume bound" on drives having only one head when data is freshly written on both sides of the disk (i.e. both volumes active).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 49% of the total text.

Volume Strategy Menu for Optical Disk Libraries

      Current implementation for storing data on optical disk
drives is to fill one side of a cartridge, "flip" the cartridge, and
then fill up the other side.  This can lead to being "volume bound"
on drives having only one head when data is freshly written on both
sides of the disk (i.e. both volumes active).

      The present method for storing information on optical disks in
an optical library is to write the data during the night in the
following sequential manner.  First one side (volume) of a mounted
optical cartridge is filled, then the cartridge is "flipped", and
finally the obverse side (volume) of that cartridge is filled.  A new
cartridge is fetched for the writing of more data once both volumes
are filled on the present cartridge.

      During the daytime shift, the data written at night is then
retrieved as needed.  Measurements of the profile of retrievals
indicate that the data retrieval is very date sensitive.  There is
quite a demand for data freshly stored on optical disks.  This demand
decays quite rapidly as the data stored on optical disks ages.

      If both sides of the optical disk have fresh data, then there
is a good change that data will be needed from both sides of the
optical disk during the same mount.  If a cartridge is loaded on an
optical disk drive with only one head or actuator, then only one side
of the optical disk could be read at a time.  Fresh or highly active
data on both sides of optical disks could periodically result in an
optical library being "volume bound".  There could be long queues for
files on the "other" side of the disk and there could be a lot of
churn caused by frequent "flipping" of the cartridge to access files
on each side.

      If the optical disk drive had two actuators, one for each side
of the mounted disk, it would be highly desirable to have fresh data
on both sides of the disk.  The drive can access both sides of the
disk without flipping.  Unlike the case of an optical drive with only
one actuator, it would improve performance to have "fresh" or highly
active data on both sides of an optical disk when the optical drive
had two actuators.

      Because of the above need to sort the writing of volumes based
on the number of actuators in the target optical disk drives, we
offer two configuration menus. These menus will help library users
who have only 1 actuator per optical drive to avoid being trapped in
a "volume bound" situation.

      The system operator, for a library having single-actuator
drives, will first be able to choose either of two volume fill
patterns as shown in Figure 1.
l
l                                                 l
l  1. SEQUENTIAL FILL PATTERN                     l
     Fill Volume A, flip cartridge, and fill
     Volume B before getting a new cartridge
   2. STAGGERED FILL PATTERN
...