ZFS Stability & MySQL (Comments Requested)

Pierre Massat depaulou at efrei.fr
Fri Apr 30 08:05:31 UTC 2010

Hi everybody,

On Thu, Apr 29, 2010 at 4:31 PM, Jason J. W. Williams
<jasonjwwilliams at gmail.com> wrote:
> I've written before that we're considering moving to FreeBSD 8 from
> OpenSolaris and are heavily reliant on ZFS. Has anyone used FreeBSDs
> ZFS implementation for a high reliability environment like a database?
> If so, what are your experiences?

I'm running MySQL 5.5 (Server version: 5.5.1-m2-log FreeBSD port:
mysql-server-5.5.1) on FreeBSD 8.0 with a quite recent kernel (FreeBSD
8.0-STABLE (GENERIC) #0: Tue Feb 23 12:38:58 UTC 2010). I've done some
tweaks to ZFS, like limiting ARC size, followed advices like
recordsize matching InnoDB page size (i'm using InnoDB on my 4Go
database). We have 11% of reads and 89% of writes and we make around
300 queries per second.

The thing is it runs well except that once, I had a very big slowdown
on MySQL : UPDATE queries were taking 30 seconds (which is actually
the timeout in my.cnf) to complete. I can't tell if it was a MySQL
problem (as i'm using something which is not release yet i think) or
if it's due to ZFS. However, after a restart, everything was back to
normal and things are running well. We have a lot of memory, 32 Go
(yes, the box is actually oversize for what we're doing right now),
and we don't stress the server so much (it has 2x XeonQuand X55xx),
and that might be a reason why it runs well (we don't push ZFS and the
server to the limits).

I hope it's useful for you. If you need anything more, please ask.

Pierre Massat

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