Comments on: Timing random disk seeks http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/ a web-log Sat, 25 May 2013 00:58:11 +0000 http://wordpress.org/?v=2.1.2 By: JC http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1071 JC Thu, 17 May 2007 15:32:18 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1071 I forgot : my drives are both Hitachi 7200 rpm. The laptop's one is 100 Gb one, the server's one 120 Go... I forgot : my drives are both Hitachi 7200 rpm.
The laptop’s one is 100 Gb one, the server’s one 120 Go…

]]> By: JC http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1076 JC Thu, 17 May 2007 15:38:13 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1076 Weired... I can't post a message with the results... Weired… I can't post a message with the results…

]]> By: ads http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1079 ads Thu, 17 May 2007 15:41:11 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1079 OK, there appears to be some problem with posting comments. Jermy or JC, can you post or mail to me (ads@wompom.org) a description of what you did and the site's response? Thanks OK, there appears to be some problem with posting comments. Jermy or JC, can you post or mail to me (ads@wompom.org) a description of what you did and the site’s response?

Thanks

]]> By: anоnуmоus http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1080 anоnуmоus Thu, 17 May 2007 15:41:24 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1080 This is reason to turn off disc cache This is reason to turn off disc cache

]]> By: ads http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1081 ads Thu, 17 May 2007 15:50:57 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1081 <b>anonymous</b>: The graph's curve would start much higher up if the readahead cache were to blame. Just to test it, I tried again and the results were within bounds: Mean: 18.5ms; Median: 17-18ms; Std dev: 11ms anonymous: The graph’s curve would start much higher up if the readahead cache were to blame. Just to test it, I tried again and the results were within bounds:

Mean: 18.5ms; Median: 17-18ms; Std dev: 11ms

]]> By: ads http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1082 ads Thu, 17 May 2007 15:55:08 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1082 <b>Jermy</b> has given me the results for one of his 500GB disks. He notes that the first time he ran the script, the median was much lower than the mean and he had a 7000-ms seek as an outlier. When he ran it again (after it had spun up) this vanished. Disk is a Seagate 500GB, Model ST3500641AS 1500 seeks of /dev/sda (465 GB) Mean: 13.7ms; Median: 12-13ms; Std dev: 3.9ms Jermy has given me the results for one of his 500GB disks. He notes that the first time he ran the script, the median was much lower than the mean and he had a 7000-ms seek as an outlier. When he ran it again (after it had spun up) this vanished.

Disk is a Seagate 500GB, Model ST3500641AS
1500 seeks of /dev/sda (465 GB)
Mean: 13.7ms; Median: 12-13ms; Std dev: 3.9ms

]]> By: Jon http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1083 Jon Thu, 17 May 2007 16:02:25 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1083 Took 25.26s for 1500 seeks of /dev/sda (74 GB) Mean: 16.8ms; Median: 14-15ms; Std dev: 8.79ms The drive is a Seagate ST3808110AS. Took 25.26s for 1500 seeks of /dev/sda (74 GB)
Mean: 16.8ms; Median: 14-15ms; Std dev: 8.79ms

The drive is a Seagate ST3808110AS.

]]> By: ads http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1084 ads Thu, 17 May 2007 16:14:06 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1084 <b>JC</b> gave me the following info: The results on my laptop (running OpenSuse 10.2) : Took 0.7388s for 1500 seeks of /dev/sda (0 GB) Mean: 0.493ms; Median: 0-1ms; Std dev: 3.29ms real 0m7.091s user 0m0.130s sys 0m0.040s The results on my server (running Debian 4.0) : Took 0.2398s for 1500 seeks of /dev/sda (0 GB) Mean: 0.16ms; Median: 0-1ms; Std dev: 0.954ms real 0m0.354s user 0m0.076s sys 0m0.028s I am rather surprised that you have such a slow access time with your disk ! JC gave me the following info:

The results on my laptop (running OpenSuse 10.2) :
Took 0.7388s for 1500 seeks of /dev/sda (0 GB)
Mean: 0.493ms; Median: 0-1ms; Std dev: 3.29ms

real 0m7.091s
user 0m0.130s
sys 0m0.040s

The results on my server (running Debian 4.0) :
Took 0.2398s for 1500 seeks of /dev/sda (0 GB)
Mean: 0.16ms; Median: 0-1ms; Std dev: 0.954ms

real 0m0.354s
user 0m0.076s
sys 0m0.028s

I am rather surprised that you have such a slow access time with your
disk !

]]> By: Branden http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1085 Branden Thu, 17 May 2007 16:21:50 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1085 Took 19.87s for 1500 seeks of /dev/sda (149 GB) Mean: 13.2ms; Median: 12-13ms; Std dev: 4.82ms Seagate ST3160827AS Took 19.87s for 1500 seeks of /dev/sda (149 GB)
Mean: 13.2ms; Median: 12-13ms; Std dev: 4.82ms

Seagate ST3160827AS

]]> By: Branden http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1086 Branden Thu, 17 May 2007 16:27:07 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1086 On my server with SCSI Ultra320 drives, Seagate Model ST3146707LC Took 13.11s for 1500 seeks of /dev/sda (136 GB) Mean: 8.74ms; Median: 7-8ms; Std dev: 4.47ms On my server with SCSI Ultra320 drives, Seagate Model ST3146707LC

Took 13.11s for 1500 seeks of /dev/sda (136 GB)
Mean: 8.74ms; Median: 7-8ms; Std dev: 4.47ms

]]> By: David Thor http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1095 David Thor Thu, 17 May 2007 21:05:16 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1095 Took 20.21s for 1500 seeks of /dev/sda (232 GB) Mean: 13.5ms; Median: 12-13ms; Std dev: 4.76ms Seagate SATA ST3250620AS Just one pointer, the results seem to vary quite a lot. After I ran the above I ran it twice again in succession. The first run looked like this: Took 22.89s for 1500 seeks of /dev/sda (232 GB) Mean: 15.3ms; Median: 12-13ms; Std dev: 6.75ms And then the second run: Took 19.98s for 1500 seeks of /dev/sda (232 GB) Mean: 13.3ms; Median: 12-13ms; Std dev: 3.7ms As you can see, performance seems to vary quite a lot so the results should be taken with a grain of salt (like most performance/benchmarking tests). The median value seems to be the one worth taking note of. Took 20.21s for 1500 seeks of /dev/sda (232 GB)
Mean: 13.5ms; Median: 12-13ms; Std dev: 4.76ms

Seagate SATA ST3250620AS

Just one pointer, the results seem to vary quite a lot. After I ran the above I ran it twice again in succession. The first run looked like this:

Took 22.89s for 1500 seeks of /dev/sda (232 GB)
Mean: 15.3ms; Median: 12-13ms; Std dev: 6.75ms

And then the second run:

Took 19.98s for 1500 seeks of /dev/sda (232 GB)
Mean: 13.3ms; Median: 12-13ms; Std dev: 3.7ms

As you can see, performance seems to vary quite a lot so the results should be taken with a grain of salt (like most performance/benchmarking tests). The median value seems to be the one worth taking note of.

]]> By: Phocean.net » Blog Archive » Measure the access time of your Hard Disk... http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1131 Phocean.net » Blog Archive » Measure the access time of your Hard Disk... Fri, 18 May 2007 22:26:46 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1131 [...] There is a nice script to measure the access time of your disk. [...] […] There is a nice script to measure the access time of your disk. […]

]]> By: Joe http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1167 Joe Sun, 20 May 2007 03:39:28 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-1167 You should send this to the hdparm maintainers. Perhaps it could be included as an example. You should send this to the hdparm maintainers. Perhaps it could be included as an example.

]]> By: ads http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-19989 ads Sun, 14 Jun 2009 16:23:17 +0000 http://blog.wompom.org/index.php/2007/05/17/timing-random-disk-seeks/#comment-19989 Just ran the script again on one partition at a time. As you migh expect, the acess time goes down but I couldn't get any better than this: Took 10.95s for 1500 seeks of /dev/md1 (1 GB) Mean: 7.3ms; Median: 6-7ms; Std dev: 3.39ms The underlying hard disk partitions showed the same results, so mirroring isn't beneficial in this case. (It's a linear, blocking script so that''s hardly surprising.) Just ran the script again on one partition at a time. As you migh expect, the acess time goes down but I couldn't get any better than this:

Took 10.95s for 1500 seeks of /dev/md1 (1 GB)
Mean: 7.3ms; Median: 6-7ms; Std dev: 3.39ms

The underlying hard disk partitions showed the same results, so mirroring isn't beneficial in this case. (It’s a linear, blocking script so that'’s hardly surprising.)

]]>