From: Neil Brown <neilb@suse.de>
To: Tomka Gergely <gergely@tomka.hu>
Cc: linux-raid@vger.kernel.org
Subject: Re: sw raid0 read bottleneck
Date: Wed, 14 Mar 2007 07:51:50 +1100 [thread overview]
Message-ID: <17911.3814.749745.77134@notabene.brown> (raw)
In-Reply-To: message from Tomka Gergely on Tuesday March 13
On Tuesday March 13, gergely@tomka.hu wrote:
> On Tue, 13 Mar 2007, Tomka Gergely wrote:
>
> > On Tue, 13 Mar 2007, Justin Piszcz wrote:
> >
> > > Have you tried increasing your readahead values for the md device?
> >
> > Yes. No real change. According to my humble mental image, readahead not a
> > too useful thing, when we read 1-4 thread with sdd. The io subsystem
> > already reading with the possible maximum speed, so don't have time to
> > read ahead. Correct me, if i wrong.
>
> I was wrong, readahead can speed things up, to 450 MBps.
Can you tell use what read-ahead size you needed?
15 drives and 64K chunks gives 960K per stripe.
The raid0 code should set the read-ahead to twice that: 1920K
which I would have thought would be enough, but apparently not.
Thanks,
NeilBrown
next prev parent reply other threads:[~2007-03-13 20:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-13 16:23 sw raid0 read bottleneck Tomka Gergely
2007-03-13 16:48 ` Justin Piszcz
2007-03-13 17:34 ` Tomka Gergely
2007-03-13 18:15 ` Tomka Gergely
2007-03-13 18:42 ` Justin Piszcz
2007-03-13 20:51 ` Neil Brown [this message]
2007-03-13 21:09 ` Tomka Gergely
2007-03-13 21:29 ` Mark Hahn
2007-03-14 18:41 ` Bill Davidsen
2007-03-14 19:32 ` Mark Hahn
2007-03-14 21:53 ` Bill Davidsen
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