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Thread: High iowait
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06-09-2005, 09:24 AM #1Newbie
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- Apr 2005
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High iowait
Hi,
I am experiencing a high iowait when running the find command as shown below.
[root@ws02 root]# time find / -name "82827635453434243" -print
real 0m12.430s
user 0m0.180s
sys 0m0.420s
[root@ws02 root]#
==TOP==
23:11:33 up 22:23, 3 users, load average: 0.01, 0.05, 0.09
134 processes: 133 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 0.0% 0.0% 0.9% 0.0% 0.0% 99.0% 0.0%
cpu00 0.0% 0.0% 1.4% 0.0% 0.0% 98.5% 0.0%
cpu01 0.0% 0.0% 0.4% 0.0% 0.0% 99.5% 0.0%
Mem: 1017328k av, 534404k used, 482924k free, 0k shrd, 120648k buff
334980k actv, 98876k in_d, 368k in_c
Swap: 1052248k av, 0k used, 1052248k free 182452k cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
10 root 15 0 0 0 0 SW 0.2 0.0 0:01 0 kupdated
15 root 15 0 0 0 0 DW 0.2 0.0 0:07 1 kjournald
19938 root 15 0 1080 1080 804 R 0.2 0.1 0:05 0 top
20116 root 18 0 512 512 344 D 0.2 0.0 0:00 0 find
1 root 15 0 512 512 452 S 0.0 0.0 0:05 0 init
2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0 migration/0
3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1 migration/1
4 root 15 0 0 0 0 SW 0.0 0.0 0:00 1 keventd
5 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
6 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1 ksoftirqd/1
9 root 25 0 0 0 0 SW 0.0 0.0 0:00 1 bdflush
7 root 15 0 0 0 0 SW 0.0 0.0 0:00 1 kswapd
8 root 15 0 0 0 0 SW 0.0 0.0 0:12 0 kscand
This machine is a CentOS 3.3. I have another RedHat 9 server but the same find command shows 0% iowait. Instead, RedHat shows around 50% system.
Would anyone know whether there might be a problem with CentOS?
Thanks in advance and regards,
Peter
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06-09-2005, 10:00 AM #2Junior Guru Wannabe
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- Dec 2004
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It seems weird you have a high io wait with nothing significant running, is there any 'big' disk writing going on ?
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06-09-2005, 10:28 AM #3Newbie
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- Apr 2005
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No, but only thing it does is reading entire disk as per the nature of the find command.
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06-09-2005, 11:53 AM #4Web Hosting Master
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Is the server new, if not you may want to check for a faulty HD.
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06-09-2005, 09:57 PM #5Newbie
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The server is new.
I don't thing it's a faulty disk since there are two disks which do the same thing.
Would this be normal for CentOS? I've never had this problem with RedHat 9 servers.
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06-10-2005, 09:03 AM #6Web Hosting Evangelist
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- Nov 2002
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This is normal on CentOs 3.4 ( I think 3.3 as well ) servers. Find command always increases the IOWAIT and it can go upto 100%. RedHat 9 doesn't supports IOWAIT by default, you need to upgrade kernel (If I am not mistaken).
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