Re: Help ZFS FreeBSD 8.0 RC2 Write performance issue

> is there anyway to safely have a log device on a ramdisk? I would assume not.

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.

--Artem