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From: Stan Hoeppner <stan@hardwarefreak.com>
To: xfs@oss.sgi.com
Subject: Re: Performance problem - reads slower than writes
Date: Wed, 01 Feb 2012 01:29:30 -0600	[thread overview]
Message-ID: <4F28E9DA.8030407@hardwarefreak.com> (raw)
In-Reply-To: <20120131202526.GJ9090@dastard>

On 1/31/2012 2:25 PM, Dave Chinner wrote:
> On Tue, Jan 31, 2012 at 02:16:04PM +0000, Brian Candler wrote:

>> Here we appear to be limited by real seeks. 225 seeks/sec is still very good
> 
> That number indicates 225 IOs/s, not 225 seeks/s.

Yeah, the voice coil actuator and spindle rotation limits the peak
random seek rate of good 7.2k drive/controller combos to about 150/s.
15k drives do about 250-300 seeks/s max.  Simple tool to test max random
seeks/sec for a device:

32bit binary:  http://www.hardwarefreak.com/seekerb
source:        http://www.hardwarefreak.com/seeker_baryluk.c

I'm not the author.  The original seeker program is single threaded.
Baryluk did the thread hacking.  Background info:
http://www.linuxinsight.com/how_fast_is_your_disk.html

Usage:   ./seekerb device [threads]

Results for a single WD 7.2K drive, no NCQ, deadline elevator:

  1 threads Results: 64 seeks/second, 15.416 ms random access time
 16 threads Results: 97 seeks/second, 10.285 ms random access time
128 threads Results: 121 seeks/second, 8.208 ms random access time

Actual output:
$ seekerb /dev/sda 128
Seeker v3.0, 2009-06-17,
http://www.linuxinsight.com/how_fast_is_your_disk.html
Benchmarking /dev/sda [976773168 blocks, 500107862016 bytes, 465 GB,
476940 MB, 500 GiB, 500107 MiB]
[512 logical sector size, 512 physical sector size]
[128 threads]
Wait 30 seconds.............................
Results: 121 seeks/second, 8.208 ms random access time (52614775 <
offsets < 499769984475)

Targeting array devices (mdraid or hardware, or FC SAN LUN) with lots of
spindles, and/or SSDs should yield some interesting results.

-- 
Stan

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  reply	other threads:[~2012-02-01  7:29 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-30 22:00 Performance problem - reads slower than writes Brian Candler
2012-01-31  2:05 ` Dave Chinner
2012-01-31 10:31   ` Brian Candler
2012-01-31 14:16     ` Brian Candler
2012-01-31 20:25       ` Dave Chinner
2012-02-01  7:29         ` Stan Hoeppner [this message]
2012-02-03 18:47         ` Brian Candler
2012-02-03 19:03           ` Christoph Hellwig
2012-02-03 21:01             ` Brian Candler
2012-02-03 21:17               ` Brian Candler
2012-02-05 22:50                 ` Dave Chinner
2012-02-05 22:43               ` Dave Chinner
2012-01-31 14:52     ` Christoph Hellwig
2012-01-31 21:52       ` Brian Candler
2012-02-01  0:50         ` Raghavendra D Prabhu
2012-02-01  3:59         ` Dave Chinner
2012-02-03 11:54       ` Brian Candler
2012-02-03 19:42         ` Stan Hoeppner
2012-02-03 22:10           ` Brian Candler
2012-02-04  9:59             ` Stan Hoeppner
2012-02-04 11:24               ` Brian Candler
2012-02-04 12:49                 ` Stan Hoeppner
2012-02-04 20:04                   ` Brian Candler
2012-02-04 20:44                     ` Joe Landman
2012-02-06 10:40                       ` Brian Candler
2012-02-07 17:30                       ` Brian Candler
2012-02-05  5:16                     ` Stan Hoeppner
2012-02-05  9:05                       ` Brian Candler
2012-01-31 20:06     ` Dave Chinner
2012-01-31 21:35       ` Brian Candler

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