From: "Bryan J. Smith" <b.j.smith@ieee.org>
To: Justin Piszcz <jpiszcz@lucidpixels.com>,
Bryan J Smith <b.j.smith@ieee.org>
Cc: xfs-bounce@oss.sgi.com, Ralf Gross <Ralf-Lists@ralfgross.de>,
linux-xfs@oss.sgi.com, linux-raid@vger.kernel.org
Subject: Re: mkfs options for a 16x hw raid5 and xfs (mostly large files)
Date: Wed, 26 Sep 2007 10:11:56 -0700 (PDT) [thread overview]
Message-ID: <673292.62672.qm@web32906.mail.mud.yahoo.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0709261223290.15219@p34.internal.lan>
Justin Piszcz <jpiszcz@lucidpixels.com> wrote:
> I have a question, when I use multiple writer threads (2 or 3) I
> see 550-600 MiB/s write speed (vmstat) but when using only 1
thread,
> ~420-430 MiB/s...
It's called scheduling buffer flushes, as well as the buffering
itself.
> Also without tweaking, SW RAID is very slow (180-200
> MiB/s) using the same disks.
But how much of that tweaking is actually just buffering?
That's a continued theme (and issue).
Unless you can force completely synchronous writes, you honestly
don't know. Using a larger size than memory is not anywhere near the
same.
Plus it makes software RAID utterly n/a in comparison to hardware
RAID, where the driver is waiting until the commit to actual NVRAM or
disc is complete.
--
Bryan J. Smith Professional, Technical Annoyance
b.j.smith@ieee.org http://thebs413.blogspot.com
--------------------------------------------------
Fission Power: An Inconvenient Solution
prev parent reply other threads:[~2007-09-26 17:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <498689.78850.qm@web32907.mail.mud.yahoo.com>
[not found] ` <Pine.LNX.4.64.0709251938400.7763@p34.internal.lan>
[not found] ` <20070926082322.GA30287@p15145560.pureserver.info>
[not found] ` <Pine.LNX.4.64.0709260442070.31289@p34.internal.lan>
[not found] ` <20070926084924.GB30287@p15145560.pureserver.info>
2007-09-26 9:52 ` mkfs options for a 16x hw raid5 and xfs (mostly large files) Justin Piszcz
2007-09-26 15:03 ` Bryan J Smith
2007-09-26 16:24 ` Justin Piszcz
2007-09-26 17:11 ` Bryan J. Smith [this message]
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