Re: FreeBSD 10 and PostgreSQL 9.3 scalability issues

Matthew Seaman <[email protected]> Tue, 18 Mar 2014 12:00:23 +0000
Newsgroups gmane.os.freebsd.performance
Message-ID <[email protected]>
On 03/18/14 03:12, Petr Janda wrote:
> ust want to share these pgbench results done by DragonFlyBSD, and would
> like some input on why these numbers look so bad and what can be done to
> improve (ie. kernel tunables etc) the performance.
> 
> http://lists.dragonflybsd.org/pipermail/users/attachments/20140310/4250b961/attachment-0001.pdf

Using ZFS as the backing for a RDBMS without:

    * Separate (fast) L2ARC devices
    * Tuning the ZFS block size to match the postgres IO block size
    * Setting primarycache to metadata
    * Tuning the ARC max so ZFS doesn't eat all the RAM
    * probably other things I can remember off-hand.

That's what is wrong.  ZFS is known to work particularly badly at the
sort of small random IOs that RDBMSes generate (mostly because of the
copy-on-write thing) without special tuning and extra hardware for
caches.  ie.  You can't construct a fair test of database performance
against other OSes/filesystems if you restrict yourself to using exactly
the same hardware.

Basically, install the FreeBSD box on UFS2 and try again.

	Cheers,

	Matthew
signature.asc (application/pgp-signature, 1 KB)
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.22 (FreeBSD)
Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/
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=fodm
-----END PGP SIGNATURE-----