[Gluster-users] Slow performance from simple tar -x && rm -r benchmark

[Chris Webb]

Bryan Whitehead <driver at megahappy.net> writes:

> I didn't see any sync's after the tar/rm commands...

By default, ext4 flushes both metadata and data every five seconds, so a
post-benchmark sync tends to make little difference on a reasonable large test,
but for completeness:

  # time bash -c 'tar xfz ~/linux-3.3-rc7.tgz; sync; rm -rf linux-3.3-rc7; sync'
  real    0m23.826s
  user    0m20.681s
  sys     0m2.392s

vs

  # time bash -c 'tar xfz ~/linux-3.3-rc7.tgz; sync; rm -rf linux-3.3-rc7; sync'

  real    4m24.067s
  user    0m24.692s
  sys     0m7.588s

showing very similar timings and the same effect.

> try using xfs instead of ext4.

I'll build the xfs tooling, add kernel support, and give this a go, but I'm
surprised you think changing the underlying filesystem would eliminate the big
gap between native and gluster performance. I could imagine it improving both
somewhat, but if anything, I'd expect a higher performance filesystem to
amplify the differences. Do you think that glusterfs does something that's
particularly expensive on ext4, much more expensive than the operations proxied
through it?

Best wishes,

Chris.