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I'm running a micro EC2 instance, and i've been seeing ... quite a lot of I/O usage (14+ million iops... for a webserver with barely 40 hits a day, plus spiders activity).

After playing with iotop, i found that Apache is writing somewhere around 6.3 megabytes, if you hit it with a browser, after a couple minutes of inactivity.

It's not Swap Memory usage.

Do you have any idea about what might be causing this?

NOTE:: I used, iotop -a -P to run this tests.

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If it's being written after every request, the most likely place for it to go is the logs. Have you tried comparing the output of

du -sh /path/to/apache/logs

before and after making a request, to see if the logs are growing by that 6MB?

If you're still having difficulty finding where it's writing to, try using lsof to see what files it has open.

  • Thanks for your reply!. Weird thing is... the size of the logfile-folder doesn't increase, at all. I'm not seeing anything weird with LSOF... honestly, i'm lost with this!. – Jorge Leandro Perez Apr 1 '13 at 17:35
  • I've figured out.... turns out that i've got APC installed. I have (no idea) why, but it's doing a lot of I/O. Thanks for your help David! – Jorge Leandro Perez Apr 1 '13 at 18:06
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Okay... found & fixed the problem. This issue is related to this post: High disk I/O when cache is used?

It turns out that APC was using a mmaped file, which caused high I/O consumption.

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