From: Bill Davidsen <davidsen@tmr.com>
To: Richard Scobie <richard@sauce.co.nz>
Cc: Mark Knecht <markknecht@gmail.com>,
Learner Study <learner.study@gmail.com>,
linux-raid@vger.kernel.org, keld@dkuug.dk
Subject: Re: Linux Raid performance
Date: Wed, 14 Apr 2010 16:50:35 -0400 [thread overview]
Message-ID: <4BC62A9B.5030706@tmr.com> (raw)
In-Reply-To: <4BB69670.3040303@sauce.co.nz>
Richard Scobie wrote:
> Mark Knecht wrote:
>
>> Once all of that is in place then possibly more cores will help, but I
>> suspect even then it probably hard to use 4 billion CPU cycles/second
>> doing nothing but disk I/O. SATA controllers are all doing DMA so CPU
>> overhead is relatively *very* low.
>
> There is the RAID5/6 parity calculations to be considered on writes
> and this appears to be single threaded. There is an experimental
> multicore kernel option I believe, but recent discussion indicates
> there may be some problems with it.
That is being polite. With that option set just doing a 'check' on a
raid-5 will generate 100s of threads and max out all cores. I was trying
to run the experimental FC13 64 bit kernel, and all of a sudden the
machine came to a crawl and the cpu use went to 95%+ on all cores. Also
drove the CPU temp way up, so I have to regard this as unsuitable for
anything but light testing.
--
Bill Davidsen <davidsen@tmr.com>
"We can't solve today's problems by using the same thinking we
used in creating them." - Einstein
prev parent reply other threads:[~2010-04-14 20:50 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-31 19:42 Linux Raid performance Learner Study
2010-03-31 20:15 ` Keld Simonsen
2010-04-02 3:07 ` Learner Study
2010-04-02 9:58 ` Nicolae Mihalache
2010-04-02 17:58 ` Learner Study
2010-04-02 11:05 ` Keld Simonsen
2010-04-02 11:18 ` Keld Simonsen
2010-04-02 17:55 ` Learner Study
2010-04-02 21:14 ` Keld Simonsen
2010-04-02 21:37 ` Learner Study
2010-04-03 11:20 ` Keld Simonsen
2010-04-03 15:56 ` Learner Study
2010-04-04 1:58 ` Keld Simonsen
2010-04-03 0:10 ` Learner Study
2010-04-03 0:39 ` Mark Knecht
2010-04-03 1:00 ` John Robinson
2010-04-03 1:14 ` Richard Scobie
2010-04-03 1:32 ` Mark Knecht
2010-04-03 1:37 ` Richard Scobie
2010-04-03 3:06 ` Learner Study
2010-04-03 3:00 ` Learner Study
2010-04-03 19:27 ` Richard Scobie
2010-04-03 18:14 ` MRK
2010-04-03 19:56 ` Richard Scobie
2010-04-04 15:00 ` MRK
2010-04-04 18:26 ` Learner Study
2010-04-04 18:46 ` Mark Knecht
2010-04-04 21:28 ` Jools Wills
2010-04-04 22:38 ` Mark Knecht
2010-04-05 10:07 ` Learner Study
2010-04-05 16:35 ` John Robinson
2010-04-04 22:24 ` Guy Watkins
2010-04-05 13:49 ` Drew
2010-04-04 23:24 ` Richard Scobie
2010-04-05 11:20 ` MRK
2010-04-05 19:49 ` Richard Scobie
2010-04-05 21:03 ` Drew
2010-04-05 22:20 ` Richard Scobie
2010-04-05 23:49 ` Roger Heflin
2010-04-14 20:50 ` Bill Davidsen [this message]
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