Iowait Issues On CentOS 7

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One of our customers has an issue where our load average on two of the boxes spikes on peak loads. What I got from testing is consistent with what they were reporting: on CentOS 7, the load spikes in hockey stick fashion, from 40-50% up to 200%, with very high iowait values. On CentOS 6, load increases and decreases linearly and the machine never slows down.

Asterisk version is, which is if course quite old (but it is what is installed). The CentOS 6 box actually has less RAM (8 Gb vs. 16 Gb), but other than that they are exactly identical in hardware configuration.

I checked the usual culprits, but to no avail. Is this a known issue?

Best regards,


One thought on - Iowait Issues On CentOS 7

  • Hi Luca,

    IO delay maybe come from Hard Disk lattency. You can exec an “lsof ”
    command to view what file asterisk proccess hold down when load spike.

    If there are some call recording, you can configure Asterisk to make it in a temp location, a RAM Disk in Linux.

    If you make hard usage of the AstDB file, you can copy it to RAM too, to avoid read/write to the disk.

    Please, read this post about lsof:

    You can view something weird in Asterisk logs when high load ? Maybe enable debug ?

    You can install and setup “atop”. Then you can review the system status after the load peak and drill down, just to the problem.

    Finally, for troubleshooting IO Wait on a Linux system, you can view this post:


    2016-11-23 12:32 GMT-03:00 Luca Pradovera :