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Segmented Left Justification: A Volume Content Reorganization Phase

IP.com Disclosure Number: IPCOM000107988D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 3 page(s) / 100K

Publishing Venue

IBM

Related People

Morey Jr, GE: AUTHOR

Abstract

Segmented left justification is a name given to a technique for optimizing contiguous free space within selected defragmentation intervals. The defragmentation intervals are storage areas on a random-access device and represent the areas of the device that are the target of a reorganization effort. The intent of free-space optimization is to increase the utility of existing free space to reduce fragmentation (extents) of subsequent file allocations.

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

Segmented Left Justification: A Volume Content Reorganization Phase

       Segmented left justification is a name given to a
technique for optimizing contiguous free space within selected
defragmentation intervals.  The defragmentation intervals are storage
areas on a random-access device and represent the areas of the device
that are the target of a reorganization effort.  The intent of
free-space optimization is to increase the utility of existing free
space to reduce fragmentation (extents) of subsequent file
allocations.

      To grasp the intent of one phase of a multi-phased process, one
must consider it in relationship to the total solution.

      The method that follows represents a solution for a partial in-
place volume reorganization of a random-access storage device.  The
output of one phase is input to the succeeding phase.
o    Creation of an in-core volume image.
     The volume image is represented by an array whose entries
reflect the contents of the reorganization target volume. The array
contains entries for directory blocks, file extents, and free-space
fragments.
o    Selection of defragmentation intervals and free-space relocation
candidates.
      The volume intervals selected for defragmentation represent the
target space that yields the best mix of benefit versus cost.  Cost
and benefit functions are predefined, and candidate intervals are
subject to the individual function constraints.  The free-space
fragments selected as candidates to receive file extents are the set
of free spaces residing outside the selected intervals.  Finally,
once the interval set is determined, an array is built with entries
representing the file extents residing in the intervals.
o    Selection of an I/O set.
      The I...