Help ZFS FreeBSD 8.0 RC2 Write performance issue

[Ivan Voras]

2009/11/12 Scott Ullrich <sullrich at gmail.com>:
> On Thu, Nov 12, 2009 at 3:19 PM, Artem Belevich <fbsdlist at src.cx> wrote:
>>
>> Log seems to be somewhat weak point in ZFS. If you lose your log
>> device, you will lose your pool. Plus, there's no way to remove log
>> device from the pool. So, once you attach some device as a log, you'd
>> better be sure that device does not disappear, because it will take
>> the rest of the pool with it. From that point, real ram-disk (i.e.
>> /dev/mdN) is definitely a recipe for disaster. External ramdisk with a
>> battery backup may be an option, but even in mirrored configuration
>> seems rather risky to me.
>>
>> http://jmlittle.blogspot.com/2008/05/problem-with-slogs-how-i-lost.html
>>
>> I'd say that SSD are probably the best fit for slog role.
>
> Indeed.   I mirrored 2 SSDs on an Areca in case I loose one of them.
> Partitioned the SSD into a log device and the rest being cache (see
> the ZFS best practices guide for details).
>
> Needless to say my performance matches that of normal writes and reads
> when using NFS now.

So in short, you are saying the to get "normal" performance out of
ZFS+NFS, the best way is to invest in an Areca and 2 SSDs :))