Gluster users - Aug 2010 - Increased performance for small files with debug/trace translator?

This has stumped me beyond belief.  I'm actually getting *much better* small
file performance with debug/trace added into the client-side volfile than
without it.  Here's what I did to test it:

  1) Downloaded latest.tar.gz (current Wordpress tarball from wordpress.org)
  2) tar xzf latest.tar.gz -C /mnt/glusterfs
  3) rm -rf /mnt/glusterfs/wordpress
  4) Added debug/trace translator in client volfile
  5) Repeated steps 2 & 3

Initial test with my normal client volfile:
  Client volfile: http://pastie.org/1072935
  untar: 32.999s
  removal: 4.540s

Second test with debug/trace translator enabled:
  Client volfile: http://pastie.org/1072951
  untar: 6.077s
  removal: 1.806s

After several test runs, the subsequent results were within a few seconds of the
initial run.  Between each run, I alternated volfiles to include and exclude the
debug/trace translator and then unmounted/mounted the GlusterFS volume  If you
compare the two volfiles, the *only* difference is that I added/removed in the
debug/trace translator.

I decided to do a third test in which I add one extra debug/trace translator for
the second server as well:

  Client volfile: http://pastie.org/1072968
  untar: 5.260s
  removal: 1.589s

The performance is marginally better with debug/trace on both bricks.

  My client details: http://pastie.org/1072993
  Server volfile: http://pastie.org/1072996

If anyone has any ideas, I'm all ears.

--
Major Hayden
major at mhtx.net

On 08/03/2010 10:24 AM, Major Hayden wrote:
> Initial test with my normal client volfile:
>   Client volfile: http://pastie.org/1072935
>   untar: 32.999s
>   removal: 4.540s
> 
> Second test with debug/trace translator enabled:
>   Client volfile: http://pastie.org/1072951
>   untar: 6.077s
>   removal: 1.806s
>
> ...
>
> If anyone has any ideas, I'm all ears.
Major, Ed Wyse, and I figured this one out on IRC.  It turns out that
when the trace translator is enabled in the client volfile, it becomes
the lowest and thus the one that's mounted . . . but it goes straight to
server01 bypassing (among other things) mirror-0.  In most cases this
would result in a "dangling volume" error, but there's a bit of a
bug in
that the only real dangling volume is iocache and that particular
translator - unlike most - doesn't produce a warning.