From: David Rees <drees76@gmail.com>
To: Bill Davidsen <davidsen@tmr.com>
Cc: Linux RAID <linux-raid@vger.kernel.org>
Subject: Re: Thoughts on using SSD
Date: Thu, 26 Mar 2009 17:51:47 -0700 [thread overview]
Message-ID: <72dbd3150903261751r911114ak16b2f9cd0d1da191@mail.gmail.com> (raw)
In-Reply-To: <49CC0B0D.5000904@tmr.com>
On Thu, Mar 26, 2009 at 4:09 PM, Bill Davidsen <davidsen@tmr.com> 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
next prev parent reply other threads:[~2009-03-27 0:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-26 23:09 Thoughts on using SSD Bill Davidsen
2009-03-27 0:51 ` David Rees [this message]
2009-03-27 4:31 ` Neil Brown
2009-03-27 4:37 ` Neil Brown
2009-04-03 23:28 ` Lars Marowsky-Bree
2009-04-09 22:26 ` Bill Davidsen
2009-04-10 9:14 ` Neil Brown
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