From: Greg Freemyer <greg.freemyer@gmail.com>
To: Goswin von Brederlow <goswin-v-b@web.de>
Cc: Jon@ehardcastle.com, linux-raid@vger.kernel.org
Subject: Re: Adding more drives/saturating the bandwidth
Date: Wed, 1 Apr 2009 12:15:23 -0400 [thread overview]
Message-ID: <87f94c370904010915xd1f5e82sca9e92c9a68884cc@mail.gmail.com> (raw)
In-Reply-To: <87skks9xg5.fsf@frosties.localdomain>
On Wed, Apr 1, 2009 at 11:59 AM, Goswin von Brederlow <goswin-v-b@web.de> wrote:
> Jon Hardcastle <jd_hardcastle@yahoo.com> writes:
>
>> --- On Tue, 31/3/09, Goswin von Brederlow <goswin-v-b@web.de> wrote:
>>> Just see if you can get a decent bandwidth from each disk:
>>>
>>> for i in /dev/sd?; do dd if=$i of=/dev/null bs=1M
>>> count=10240 & done
>>> iostat -k 10
>>>
>>>
>>> Halving the bus speed gives you a reasonable low
>>> expectation of how
>>> much data you should be able to pull of the disks. If your
>>> disks can't
>>> even fill half the bus bandwidth you certainly can cope
>>> with more
>>> disks or something is seriously wrong.
>>>
>>> MfG
>>> Goswin
>
> Perfectly save. Just don't do it the other way around:
>
> !!!WARNING WRITE TEST!!!
>
> for i in /dev/sd?; do dd if=/dev/zero of=$i bs=1M count=10240 & done
> iostat -k 10
Be advised: on some suse kernels /dev/zero is known to have a
performance bug that would keep it from saturating a PCI-express bus.
I think it was the kernel they had about a year ago (10.3 release).
Greg
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next prev parent reply other threads:[~2009-04-01 16:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-26 12:43 Adding more drives/saturating the bandwidth Jon Hardcastle
2009-03-30 15:40 ` Goswin von Brederlow
2009-03-30 16:28 ` Nagilum
2009-03-31 8:23 ` Jon Hardcastle
2009-03-31 13:05 ` Greg Freemyer
2009-03-31 21:07 ` Goswin von Brederlow
2009-04-01 8:15 ` Jon Hardcastle
2009-04-01 8:56 ` Jon Hardcastle
2009-04-01 15:59 ` Goswin von Brederlow
2009-04-01 16:15 ` Greg Freemyer [this message]
2009-04-01 14:56 ` Andrew Burgess
2009-04-01 15:17 ` David Lethe
2009-04-01 18:06 ` Goswin von Brederlow
2009-04-01 18:57 ` Richard Scobie
2009-04-03 20:42 ` Goswin von Brederlow
2009-04-03 21:06 ` Robin Hill
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