From: David Nellans <david@nellans.org>
To: tech8891 <tech8891@163.com>
Cc: fio@vger.kernel.org
Subject: Re: very unstable IOPS in the same test on the same machine
Date: Thu, 02 Jan 2014 21:37:16 -0600 [thread overview]
Message-ID: <52C6306C.8000704@nellans.org> (raw)
In-Reply-To: <12ab081a.346f.14356185dd9.Coremail.tech8891@163.com>
On 01/02/2014 09:14 PM, tech8891 wrote:
> Thanks for your answer， Nellans! I think 31k IOPS should be because the RAID card cache. Seems we have 394MB cache in this controller, which is enough hold the 2 * 128M data.
While I'm not a megaraid expert it looks like you're using 4 seagate 10k
rpm drives with a 3ms random read time (looked up specs from seagat)
drives in a raid 10 with a stripe size of 64KB. Raid 10
performance affects aside, you essentially have a raid-0 of two drives.
At absolute best, each of your drives might be able to do 333 IOPS at a
small random I/O size. 100% raid-0 efficiency would give you 666 IOPS
peak. So getting 400 IOPS with random block sizes within a 1.2G range
(where the disk heads don't have to move much thus speeding up seek
time), seems very reasonable. Nothing seems obviously wrong to me with
the performance you're seeing.
prev parent reply other threads:[~2014-01-03 3:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-02 9:58 very unstable IOPS in the same test on the same machine tech8891
2014-01-02 15:40 ` David Nellans
2014-01-02 17:04 ` Roger Sibert
2014-01-03 3:14 ` tech8891
2014-01-03 3:37 ` David Nellans [this message]
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