Re: Thoughts on using SSD

On Thu, Mar 26, 2009 at 4:09 PM, Bill Davidsen [off-list ref] wrote:

If I were to create a small raid device, raid1, made of the 4GB Ssd and 4GB
of SATA space, if I made the SATA write-mostly and write-behind, and put the
journal for my raid arrays (and bitmaps?) that seems likely to provide a
significant performance gain in small storage.

Am I missing anything here? Is there an obvious drawback I'm missing?

Yeah, the fact that it doesn't seem to be possible to take advantage
of the write-behind feature? :-p

Besides fsync, I think it may have something to do with barriers.  As
in, when you flush a barrier, that causes entire cache to get flushed
to disk, including your write-behind disk.

Hopefully Neil can chime in here.  I found this thread from a while
back which seemed relevant, but I haven't been able to digest the
whole thing yet: http://lkml.org/lkml/2007/5/25/71

-Dave