Benchmark : ext3 vs reiser4 and effects of fragmentation.

[Will Smith <will@willsmith.org>]

I've spent the last 2 days coding and running benchmarks
on the effects of fragmentation on both ext3 and
reiser4 performance.

Explanation and source code is at
http://www.willsmith.org/opensource/reiser4/fragperf/

Results and graphs are at
http://www.willsmith.org/opensource/reiser4/fragperf/test1/


Dataset is a kernel source (~200Mb) in a small 350Mb
partition, with random deletes, copies and overwrites
to cause fragmentation.

In conclusion:

1) reiser4 is slightly faster than ext3 in some cases, but
    much faster in others (no surprise).  However,
    deletes are slightly slower.

2) ext3 degrades badly from fragmentation when running
    ordered (non-random) access patterns.  reiser4
    also degrades but not as much.

3) the repacker can bring performance of reiser4 back
    to full speed, but only if run several times.

4) the repacker is not yet stable - I had to run fsck
    a few times after repacking, and once got a kernel
    stack trace during repacking resulting in an
    un-unmountable filesystem.


I'll gladly rerun with different parameters and/or change
the script if requested.


Will Smith