More zfs benchmarks

[Freddie Cash]

On Mon, Feb 15, 2010 at 9:51 AM, Jonathan Belson <jon at witchspace.com> wrote:

> On 14/02/2010 17:28, Jonathan Belson wrote:
>
>> After reading some earlier threads about zfs performance, I decided to
>> test my own server.  I found the results rather surprising...
>>
>
> Thanks to everyone who responded.  I experimented with my load.conf
> settings, leaving me with the following:
>
> vm.kmem_size="1280M"
> vfs.zfs.prefetch_disable="1"
>
> That kmem_size seems quite big for a machine with only (!) 2GB of RAM, but
> I wanted to see if it gave better results than 1024MB (it did, an extra
> ~5MB/s).
>

For a system with 2 GB of RAM, and possibly slow harddrives, consider adding
a "cache" vdev (L2ARC).  The 4 GB and larger USB flash drives are getting to
be pretty fast for reads (which is what the L2ARC is for).

On my home system, which is a 32-bit FreeBSD 8-STABLE box with a 3.0 GHz P4
and 2 GB of RAM, adding a 4 GB Transcend JetFlash has done wonders for
improving stability and read speed.  Most of my apps now load from the USB
stick instead of the slow raidz1 vdev (3x 120 GB SATA drives).

Haven't done any real benchmarks yet (still upgrading to KDE 4.4), but
things feel smoother, and it hasn't locked up since adding the USB stick.
 On this box, running ktorrent 24/7 used to lock up the box after 3-5 days
(can't even toggle numlock).

This box uses a kmem_max of 1 GB, and an arc_max of 512 MB.  With a 4 GB
L2ARC.  :)

-- 
Freddie Cash
fjwcash at gmail.com