ZFS-FreeBSD + postgresql performance

[Ivailo.TANUSHEFF at raiffeisen.bg]

owner-freebsd-fs at freebsd.org wrote on 23.10.2013 23:57:57:

> From:
> 
> Michael Schmiedgen <schmiedgen at gmx.net>
> 
> To:
> 
> Mark Felder <feld at FreeBSD.org>, Albert Shih <Albert.Shih at obspm.fr>, 
> pgsql-admin at postgresql.org, freebsd-fs at freebsd.org, 
freebsd-jail at freebsd.org, 
> 
> Date:
> 
> 23.10.2013 23:58
> 
> Subject:
> 
> Re: ZFS-FreeBSD + postgresql performance
> 
> Sent by:
> 
> owner-freebsd-fs at freebsd.org
> 
> On 10/23/13 19:14, Mark Felder wrote:
> > On Wed, Oct 23, 2013, at 11:25, Albert Shih wrote:
> >> My question is about the performance, I known ZFS eat all memory he 
can
> >> have (or almost), so what append when we run database like postgresql 
and
> >> jail ? (it's also the reason of 96 Go ram).
> >>
> >> Sorry for cross-posting but it's about 3 differents things....
> >>
> >
> > To my understanding the solution is to change the primarycache to
> > "metadata" for any ZFS filesystem that you do not want ZFS to heavily
> > cache in memory.
> >
> > Example:
> >
> > # zfs set primarycache=metadata tank/usr/local/pgsql
> 
> In addition to this it is recommended to set the recordsize
> to the fixed value of 8k on dataset creation.
> 
> Michael
> 

I would also recommend to use 4K sector size using gnop and zpool 
export/import.
I agree that using fixed recordsize is a must when you have databases and 
you have DB on each jail.
Also there are a bunch of sysctl parameters you may want to play with, 
mostly about tuning the memory usage.

Also it might be an idea to use partitions on disks and:
1. Use first 1-2G on each disk for swap (just in case).
2. Use the rest of the disk for 4K aligned and 4K sector size partition, 
labelled in some way (I use disk ID as label, for easy identification).

Best regards,
Ivailo Tanusheff

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