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Date:      Fri, 2 Sep 2011 09:29:33 -0700
From:      David Brodbeck <brodbd@uw.edu>
To:        freebsd-fs@freebsd.org
Subject:   ZFSv28+NFSv4 poor file creation performance, "sync=disabled" has no effect
Message-ID:  <CAHHaOuY=BEMrhYuzXtD5AtXG7niLXEO1yhO5P4EimcsLuTrLXw@mail.gmail.com>

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I originally posted this on FreeBSD-questions, but it was suggested that I
bring it here.
I'm testing FreeBSD 9.0-BETA with an eye toward eventually using
FreeBSD 9.0 to replace some existing OpenSolaris 2008.11
installations.  I've found NFS file creation performance (as measured
by Bonnie++) is equally slow for both with default settings.  However,
on OpenSolaris I disable the ZIL to improve file creation performance.
 This tuning parameter was removed from FreeBSD 9.0; its replacement
is supposed to be the per-filesystem flag "sync", but setting this
flag seems to have no effect.

I did recompile the FreeBSD kernel without debugging features before
doing the tests, so I don't think this is a case of debugging code
slowing things down.

Here's the relevant data; these are all from bonnie++'s "sequential
create" benchmark.  The NFS client was RedHat Enterprise Linux 5.6.

OpenSolaris 2008.11, default settings: 58/second
OpenSolaris 2008.11, with "zil_disable=1": 1258/second

FreeBSD 9.0-BETA, default settings: 107/second
FreeBSD 9.0-BETA, with "sync=disabled": 106/second


So it appears the "sync" ZFS parameter has no effect in FreeBSD.  Has
anyone else seen this?  Is there a way to improve NFS file creation
performance now that zil_disable has been removed?

-- 
David Brodbeck
System Administrator, Linguistics
University of Washington



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