From: Eric Sandeen <sandeen@redhat.com>
To: Shapor Naghibzadeh <shapor@shapor.com>
Cc: ext4 development <linux-ext4@vger.kernel.org>
Subject: Re: More testing: 4x parallel 2G writes, sequential reads
Date: Wed, 07 Nov 2007 21:06:52 -0600 [thread overview]
Message-ID: <47327D4C.7070604@redhat.com> (raw)
In-Reply-To: <20071108001434.GB16884@yzf.shaptech.com>
Shapor Naghibzadeh wrote:
> On Wed, Nov 07, 2007 at 04:42:59PM -0600, Eric Sandeen wrote:
>> Again this was on a decent HW raid so seek penalties are probably not
>> too bad.
>
> You may want to verify that by doing a benchmark on the raw device. I
> recently did some benchmarks doing random I/O on a Dell 2850 w/ a PERC
> (megaraid) RAID5 w/ 128MB onboard writeback cache and 6x 15krpm drives
> and noticed appoximately one order of magnitude throughput drop on
> small (stripe-sized) random reads versus linear. It maxed out at ~100
> random read IOPs or "seeks/sec" (suprisingly low).
>
> Out of curiousity, how are you counting the seeks?
Chris Mason's seekwatcher (google can find it for you) is doing the
graphing, it uses blocktrace for the raw data.
-Eric
> Shapor
prev parent reply other threads:[~2007-11-08 3:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-07 22:42 More testing: 4x parallel 2G writes, sequential reads Eric Sandeen
2007-11-07 23:09 ` Andreas Dilger
2007-11-07 23:18 ` Eric Sandeen
2007-11-08 3:39 ` Eric Sandeen
2007-11-07 23:17 ` Alex Tomas
2007-11-08 0:14 ` Shapor Naghibzadeh
2007-11-08 3:06 ` Eric Sandeen [this message]
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