From: Stan Hoeppner <stan@hardwarefreak.com>
To: xfs@oss.sgi.com
Subject: Re: A little RAID experiment
Date: Tue, 17 Jul 2012 21:18:18 -0500 [thread overview]
Message-ID: <50061CEA.4070609@hardwarefreak.com> (raw)
In-Reply-To: <20120717052621.GB23387@dastard>
On 7/17/2012 12:26 AM, Dave Chinner wrote:
...
> I bet it's single threaded, which means it is:
The data given seems to strongly suggest a single thread.
> Which means throughput is limited by IO latency, not bandwidth.
> If it takes 10us to do the write(2), issue and process the IO
> completion, and it takes 10us for the hardware to do the IO, you're
> limited to 50,000 IOPS, or 200MB/s. Given that the best being seen
> is around 35MB/s, you're looking at around 10,000 IOPS of 100us
> round trip time. At 5MB/s, it's 1200 IOPS or around 800us round
> trip.
>
> That's why you get different performance from the different raid
> controllers - some process cache hits a lot faster than others.
...
> IOWs, welcome to Understanding RAID Controller Caching Behaviours
> 101 :)
It would be somewhat interesting to see Stefan's latency and throughput
numbers for 4/8/16 threads. Maybe the sysbench "--num-threads=" option
is the ticket. The docs state this is for testing scheduler
performance, and it's not clear whether this actually does threaded IO.
If not, time for a new IO benchmark.
--
Stan
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next prev parent reply other threads:[~2012-07-18 2:18 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-25 8:07 A little RAID experiment Stefan Ring
2012-04-25 14:17 ` Roger Willcocks
2012-04-25 16:23 ` Stefan Ring
2012-04-27 14:03 ` Stan Hoeppner
2012-04-26 8:53 ` Stefan Ring
2012-04-27 15:10 ` Stan Hoeppner
2012-04-27 15:28 ` Joe Landman
2012-04-28 4:42 ` Stan Hoeppner
2012-04-27 13:50 ` Stan Hoeppner
2012-05-01 10:46 ` Stefan Ring
2012-05-30 11:07 ` Stefan Ring
2012-05-31 1:30 ` Stan Hoeppner
2012-05-31 6:44 ` Stefan Ring
2012-07-16 19:57 ` Stefan Ring
2012-07-16 20:03 ` Stefan Ring
2012-07-16 20:05 ` Stefan Ring
2012-07-16 21:27 ` Stan Hoeppner
2012-07-16 21:58 ` Stefan Ring
2012-07-17 1:39 ` Stan Hoeppner
2012-07-17 5:26 ` Dave Chinner
2012-07-18 2:18 ` Stan Hoeppner [this message]
2012-07-18 6:44 ` Stefan Ring
2012-07-18 7:09 ` Stan Hoeppner
2012-07-18 7:22 ` Stefan Ring
2012-07-18 10:24 ` Stan Hoeppner
2012-07-18 12:32 ` Stefan Ring
2012-07-18 12:37 ` Stefan Ring
2012-07-19 3:08 ` Stan Hoeppner
2012-07-25 9:29 ` Stefan Ring
2012-07-25 10:00 ` Stan Hoeppner
2012-07-25 10:08 ` Stefan Ring
2012-07-25 11:00 ` Stan Hoeppner
2012-07-26 8:32 ` Dave Chinner
2012-09-11 16:37 ` Stefan Ring
2012-07-16 22:16 ` Stefan Ring
2012-10-10 14:57 ` Stefan Ring
2012-10-10 21:27 ` Dave Chinner
2012-10-10 22:01 ` Stefan Ring
-- strict thread matches above, loose matches on Subject: below --
2012-04-26 22:33 Richard Scobie
2012-04-27 21:30 ` Emmanuel Florac
2012-04-28 4:15 ` Richard Scobie
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