ZFS on a single disk?

[Alexander Leidinger]

Quoting Jeremy Chadwick <freebsd at jdc.parodius.com> (from Tue, 1 Mar  
2011 16:16:50 -0800):

> On Wed, Mar 02, 2011 at 12:00:24AM +0000, Dr Josef Karthauser wrote:
>> On 1 Mar 2011, at 23:49, Mark Blackman wrote:
>> >
>> > On 1 Mar 2011, at 23:27, Dr Josef Karthauser wrote:
>> >
>> >> Does it make sense to run zfs on a single disk?
>> >>
>> >> I'm setting up a FreeBSD host over at a Xen provider, with a  
>> single 80GB disk image. Ideally I'd like to run ZFS on this system,  
>> for snapshot and flexible creation of filesystems and quotas. Has  
>> anyone got any recommendations for me in this regard? Am I crazy?
>> >
>> > Not crazy, I do this as well, all the time just to get the  
>> management capabilities and
>> > leave hardware RAID to manage the availability.
>> >
>> > - Mark
>>
>> Any idea what the performance implications are? Can I get away  
>> without a ZIL or ARC and still get a decent performance?
>
> Do not disable the ZIL.  I hate referring to the Solaris documentation
> for FreeBSD, but it applies:
>
> http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Disabling_the_ZIL_.28Don.27t.29
>
> And you cannot disable the ARC, so just tune it appropriately (which
> you'll need to do on FreeBSD anyway).  In fact, by getting rid of the
> ARC (as you proposed), you would suffer worse performance than if you
> had it in use.

If you are not satisfied with the performance, you can add a USB  
memory stick as a cache device to the pool. See the following link to  
get a glue about what to expect and when it makes sense and when not:
    http://www.leidinger.net/blog/2010/02/10/making-zfs-faster/

Bye,
Alexander.

-- 
To add insult to injury.
		-- Phaedrus

http://www.Leidinger.net    Alexander @ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org       netchild @ FreeBSD.org  : PGP ID = 72077137