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Re: removing an ext2fs file forces disk activity

From: Jon Arney
Subject: Re: removing an ext2fs file forces disk activity
Date: Tue, 26 Mar 2002 11:04:14 -0700

I noticed this activity as well quite a while back.  It's not
limited to 'rm'.  I also wrote a similar test script with 'mv'
and even a 'hello-world' with 'rename' to continuously rename
a file from 'foo.0' to foo.fffffff and the drive light just went
_crazy_.  As you observed, the same sort of thing under Linux
operates almost entirely in disk and fileystem cache.

I understand the goals of having disk syncrhonization performed
in the proper order to avoid disk inconsistencies.  I also,
however, agree with Adam that something less than "optimal"
might be better than nothing at all.

> Linux, IIRC, simply ignores the issue entirely, and hopes you don't
> get screwed.

And when I get screwed, e2fsck fixes it for me most of the time.

For instance, a simple LRU cache algorithm implemented in
'libstore' might provide a large performance advantage with
the caveat that it might occasionally lead to disk inconsistencies.
This is a performance trade-off I'm willing to make.  i.e. I'm
willing to gamble the risk of data loss on some filesystems in
exchange for, say, building 'glibc' more than once in 24 hours
(slight exageration).

Perhaps I'll pull out 'bonnie' and some other test programs to
provide some relative performance numbers under the Hurd v.s.
Linux just to quantify the trade-off being made.

Jonathan S. Arney
Software Engineer
Some people call me a nihilist.
That would be true except I don't believe in nihilism.

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