Any disk de-fragmenters out there?
Alan's Home for Wayward Notes File.
alan at shodha.dec.com
Thu Nov 30 13:24:59 AEST 1989
In article <2095 at compugen.>, john at compugen. (John Beaudin) writes:
> Something along the lines of Raxco's Rabbit, or DiskKeeper, or Squeezpak.
ULTRIX(+) uses the Berkeley Fast File System [1] which
is in a way is very resistant to fragmentation. Of
course "very resistant" to fragmentation doesn't mean
that it can't happen. A problem I have considered from
time to time is how to determine whether a file system
is badly enough fragmented to warrant trying to clean
it up. It is not only a matter of having a file with
blocks scattered all over, also one of having FILES
scattered all over and the access patterns of the I/O
to those files.
It has been shown that frequently accessed file systems
should live towards the middle of a disk to get the best
access times. I would guess that if you could determine
which files are the most frequently accessed that you
should arrange for them to live closest to the center.
A defragmenter for the FFS wouldn't isn't a "simple" matter
of compacting all the blocks of a file into one nice little
area, but it is an interesting problem if it exists.
[1] - A Fast File System for UNIX*, revised July 27 1983
Marshall Kirk McKusick, William N. Joy, Samuel J. Leffler,
Robert S. Fabry.
(*) UNIX is a trademark of AT&T.
(+) ULTRIX is a trademark of Digital Equipment Corporation.
--
Alan Rollow alan at nabeth.enet.dec.com
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