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Full Discussion: Raid0 array stresses only 1 disk out of 3
Top Forums UNIX for Dummies Questions & Answers Raid0 array stresses only 1 disk out of 3 Post 302970716 by chebarbudo on Monday 11th of April 2016 06:47:15 AM
Old 04-11-2016
Raid0 array stresses only 1 disk out of 3
Hi there,

I've setup a raid0 array of 3 identical disks using :
Code:
mdadm --create --verbose /dev/md0 --level=stripe --raid-devices=3 /dev/sdb1 /dev/sdc1 /dev/sdd1

I'm using dstat to monitor the disk activity :
Code:
dstat --epoch -D sdb,sdc,sdd --disk-util 30

The results show that the stress is not evenly split (stripped) across the 3 disks:
Code:
2016-04-11 09:35:30 |   26%   28%   27%
[...]
2016-04-11 10:15:00 |    0%  100%    0%
2016-04-11 10:15:30 |    0%    3%   97%
2016-04-11 10:16:00 |    0%    0%   81%
2016-04-11 10:16:30 |    0%    0%  100%
2016-04-11 10:17:00 |    0%    0%   30%
[...]
2016-04-11 11:28:30 |    0%    0%   55%
2016-04-11 11:29:00 |    0%    0%   49%
2016-04-11 11:29:30 |    0%    0%   31%
2016-04-11 11:30:00 |    0%    0%   73%
2016-04-11 11:30:30 |    0%    0%    4%
2016-04-11 11:31:00 |    0%    0%   99%
[...]
2016-04-11 11:32:00 |    0%    0%   81%
2016-04-11 11:32:30 |    0%    0%   43%
[...]
2016-04-11 11:43:30 |    0%   93%    0%
2016-04-11 11:44:00 |    0%  100%    0%
2016-04-11 11:44:30 |    0%   97%    0%
2016-04-11 11:45:00 |    0%  100%    0%
2016-04-11 11:45:30 |    0%   10%    0%
[...]
2016-04-11 11:51:30 |    0%   79%    0%
2016-04-11 11:52:00 |    0%  100%    0%
2016-04-11 11:52:30 |    1%    9%    1%
2016-04-11 11:53:00 |    0%  100%    0%
2016-04-11 11:53:30 |    0%   98%    0%
2016-04-11 11:54:00 |    0%   30%    0%
2016-04-11 11:54:30 |    1%    1%    1%
2016-04-11 11:55:00 |    2%    3%    2%
[...]
2016-04-11 12:07:30 |    0%   68%    1%
2016-04-11 12:08:00 |    0%  100%    0%
2016-04-11 12:08:30 |    0%  100%    0%
2016-04-11 12:09:00 |    0%   38%    0%
[...]
2016-04-11 12:23:00 |    0%   84%    1%
2016-04-11 12:23:30 |    0%   58%    0%
[...]
2016-04-11 14:17:00 |    0%   43%    0%
2016-04-11 14:17:30 |    0%   99%    0%
2016-04-11 14:18:00 |    0%  100%    0%
2016-04-11 14:18:30 |    1%    6%    1%
[...]
2016-04-11 14:46:30 |    2%    2%    1%
[...]
2016-04-11 14:48:00 |    1%    9%    1%
2016-04-11 14:48:30 |    0%  100%    0%
2016-04-11 14:49:00 |    0%   96%    0%
2016-04-11 14:49:30 |    0%  100%    0%
2016-04-11 14:50:00 |    0%   99%    0%
2016-04-11 14:50:30 |    0%  100%    0%
2016-04-11 14:51:00 |    0%   41%    0%
2016-04-11 14:51:30 |    0%  100%    0%
2016-04-11 14:52:00 |    2%   18%    2%
[...]
2016-04-11 15:23:30 |    3%    5%    3%
[...]
2016-04-12 09:25:30 |    4%    3%    3%

Do you have an explanation?
Thanks for your help.

Santiago

OS : Debian Wheezy 7.4
Disks : ATA Hitachi HUA72302, 2000GB
Last edited by chebarbudo; 04-12-2016 at 07:00 AM.. Reason: edited command
 

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