tlug: Linux defrag program: is it safe?

["Stephen J. Turnbull" <turnbull@example.com>]

>>>>> "Dennis" == Dennis McMurchy <denismcm@example.com> writes:

    Dennis> 	The latest release of the Linux filesystem
    Dennis> defragmenter, defrag-0.70,

    Dennis>   Has anyone used this?  I would hesistate to unleash
    Dennis> something like this on my actual (non-experimental) Lignux
    Dennis> partition, which is what really needs it (although
    Dennis> fragmentation is still reported at under 5% - I would
    Dennis> imagine after all this time, it's pretty bad).

It's not clear to me what this is good for.  I rather doubt that at
that level of fragmentation defragmenting would give any performance
benefits; only if you have a need for large contiguous files would you
want it.  The only common use for those that I know of is swapfiles.
High performance databases and the like would want it, and HD images
for i/o bound CD-based (ie, slow) multi-media presentations too, I'm
guessing.

But the reason for defragging in MSDOG/Windoze is quite different:
poor (or no) caching means that you're reading and rereading the same
executables and overlays over and over again.  Single-tasking means
that everything waits for the disk read.  Then fast-reading contiguous
file layouts are a big win.  But in Unix the time-consuming part of
running a program is dynamic linking to the libraries which are
usually already in memory (and for major applications, eg, under X,
setting up resource databases and realizing widgets).  The disk
intensive aspects of virtual memory are already optimized by using
page-oriented organization rather than file-oriented organization.

I'd say you don't need it until somebody says its safe and does good
things for you.

Steve
Next TLUG meeting is Saturday Dec. 13, 1997  (possibly Nov. 13?)
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