From: Bill Davidsen <davidsen@tmr.com>
To: Mikael Abrahamsson <swmike@swm.pp.se>
Cc: Roman Mamedov <roman@rm.pp.ru>, Shaochun Wang <scwang@ios.ac.cn>,
"linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>
Subject: Re: Write-intent bitmap decreases or increase performance of RAID5?
Date: Sun, 04 Jul 2010 20:11:23 -0400 [thread overview]
Message-ID: <4C31232B.1080700@tmr.com> (raw)
In-Reply-To: <alpine.DEB.1.10.1006300857300.8623@uplift.swm.pp.se>
Mikael Abrahamsson wrote:
> On Wed, 30 Jun 2010, Roman Mamedov wrote:
>
>> This is not necessary. See the dd man page about the conv=fdatasync
>> switch.
>> You can even test with just 256 MB this way, and still get an extremely
>> accurate result.
>
> You're right, for writing this is ok. For read tests it's important to
> use more than ram though, to avoid doing performance testing from
> block cache instead of from the actual drives.
>
See /proc/sys/vm/drop_caches.
--
Bill Davidsen <davidsen@tmr.com>
"We can't solve today's problems by using the same thinking we
used in creating them." - Einstein
next prev parent reply other threads:[~2010-07-05 0:11 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-29 20:11 Write-intent bitmap decreases or increase performance of RAID5? Shaochun Wang
2010-06-30 5:18 ` Roman Mamedov
2010-06-30 5:54 ` Mikael Abrahamsson
2010-06-30 5:59 ` Roman Mamedov
2010-06-30 6:58 ` Mikael Abrahamsson
2010-06-30 8:23 ` Roman Mamedov
2010-06-30 18:31 ` CoolCold
2010-07-05 0:11 ` Bill Davidsen [this message]
2010-07-01 6:40 ` Shaochun Wang
2010-07-01 20:30 ` Majed B.
2010-07-01 20:50 ` Roman Mamedov
2010-07-05 0:14 ` Bill Davidsen
2010-07-01 20:49 ` Roman Mamedov
2010-07-02 11:13 ` John Robinson
2010-07-05 0:17 ` Bill Davidsen
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