Help ZFS FreeBSD 8.0 RC2 Write performance issue

[Artem Belevich]

On Thu, Nov 12, 2009 at 6:13 PM, Sam Fourman Jr. <sfourman at gmail.com> wrote:
> so you are suggesting that it is possible that 2x SSD disks would get
> me the other 60MB/sec

I guess you can test what SSDs would buy you in terms of performance.
Disable ZIL and run your performance test. If ZIL is what's causing
issues, then you will see a speedup. In this case proper log on SSDs
should bring your performance fairly close to those numbers, provided
SSDs can handle your write rate. If disabling ZIL does not help much,
then separate log device will not help much either.

On a side note, log device does not have to be big. According to Sun
you'll need ~1/2 of your physical memory size:
http://docs.sun.com/app/docs/doc/819-5461/gfgaa?a=view

Given that typical SSDs these days are quite a bit larger than your
typical RAM size, you may use the rest of the SSD as L2ARC.

--Artem