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
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