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Partial Floating Home Cell for Single Gripper Picker Libraries

IP.com Disclosure Number: IPCOM000108921D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 95K

Publishing Venue

IBM

Related People

Willson, LD: AUTHOR [+2]

Abstract

Libraries of removable media use one or more robotic pickers, each of which having one or more media grippers, to move media in a matrix of cartridge slots and devices. Those libraries having a single-gripper picker in each box are preferred due to cost considerations. For mechanical reliability reasons, it is desirable to restrict the motion of the single-gripper picker within the matrix of cartridges and devices to non-diagonal motion. Specifically, the picker may move vertically within any column of the cartridge-device matrix. To switch between columns within the cartridge-device matrix, the picker must make a special move to the lower or upper row of the matrix and translate to an adjoining column. (Image Omitted)

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This is the abbreviated version, containing approximately 52% of the total text.

Partial Floating Home Cell for Single Gripper Picker Libraries

       Libraries of removable media use one or more robotic
pickers, each of which having one or more media grippers, to move
media in a matrix of cartridge slots and devices. Those libraries
having a single-gripper picker in each box are preferred due to cost
considerations.  For mechanical reliability reasons, it is desirable
to restrict the motion of the single-gripper picker within the matrix
of cartridges and devices to non-diagonal motion.  Specifically, the
picker may move vertically within any column of the cartridge-device
matrix.  To switch between columns within the cartridge-device
matrix, the picker must make a special move to the lower or upper row
of the matrix and translate to an adjoining column.

                            (Image Omitted)

      Within this hierarchy of picker motion constraints, we propose
a means of improving the cycle time of the picker in a library having
two columns and a plurality of rows, cartridges, and devices.  These
devices may utilize any form of media, magneto-optical, write-once
optical, magnetic tape, etc.

      The cartridge disposition of KEEP means that the library will
KEEP inactive cartridges in the devices pending the arrival of new
mount requests.  When the library box has a cartridge disposition of
KEEP and is undergoing a scenario of the random reads of small files,
the box is picker bound.  Specifically, this means that the picker is
the critical path of its respective box.

      For an M/M/1 queue, any activity which reduces the picker cycle
time will reduce both the service time and the queue time, as shown
in Equations 1 and 2.  Thus, more improvement is gained in the
average response time than merely the improvement made to the picker
cycle time.  The total amount of improvement is gained in the average
response time than merely the improvement made to the picker cycle
time.  The total amount of improvement depends on the picker
utilization, which is a function of the actual cartridge fetches per
hour, as shown in Equation 2.
      Rt = St + Queue Time (1)
                       U
      Rt = St + St * ------- (2)
                     1 - U
where    ...