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High Loads/High IOWAIT - any ideas?

Discussion in 'General Discussion' started by Brook, Jul 18, 2007.

  1. Brook

    Brook Member

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    For some reason my server occasionally get's very high loads bringing it to a slow halt. Any ideas why this might be? nothing in top stats seems to point to anything apart from the high IOWAIT.

    Then IOWAIT suddenly drops back to zero and then in top I get this:


    With the CPU % at 93.3 for command http.

    Then cpanel will automagically restart cpsrvd and loads will eventually come back down again.

    Could this be a dos attack? Any ideas what commands I should use to see what's causing this?

    My forums software sends me a report to say 'MySQL server has gone away' - could that be a hint as to what it is?

    The whole thing lasts about 20 minutes or so and seems to be happening more frequently.

    Would appreciate any help on the matter.
     
  2. mtindor

    mtindor Active Member

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    Look at your Apache Server Status in WHM when this is happening and you might be able to get an idea [if it is Apache] what site is being hit so hard and by whom to cause that.

    SQL going away could mean that MySQL is the problem, or it could just simply mean that because of the load on the server at that time MySQL cannot effectively communicate with PHP/Apache.

    Mike
     
  3. trhosting.net

    trhosting.net Member

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    What is your operating system and kernel version?
     
  4. Brook

    Brook Member

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    Thanks Both...

    CENTOS Enterprise 3.8 i686
    Kernel: 2.4.21-47.0.1.EL

    WHM 11.2.0 cPanel
    WHM X v3.1.0
     
  5. Frimon86

    Frimon86 BANNED

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    What kind of mysql version are you running? Have you tried to make sure all the scripts you are hosting are up to date? I dont think it's a dosattack
     
  6. Brook

    Brook Member

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    I don't think it's a dos attack either, here is some further info:
     
  7. mtindor

    mtindor Active Member

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    Showing us specs and OS/Cpanel versions really isn't going to help in any way.

    You have to wait til it is happening and learn how to use some other command line tools to determine what is going on at the time it is happening.

    Mike
     
  8. Freezer

    Freezer Member

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    Swap: 1052248k av, 717024k used, 335224k free 85492k cached

    Look @ your swap usage. Your server is swapping into/from harddrive. Place more memory in your server, IOwait is the time waiting on harddrive.
    So increase your memory (with at least 1 gb, because you are using 700mb in swap)
     
  9. trhosting.net

    trhosting.net Member

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    Upgrade your ram and you may try upgrading your kernel.
     
  10. Frimon86

    Frimon86 BANNED

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    Yeah it may not have enough ram in your server, hopfully it wont bust your wallet just to upgrade.
     
  11. jayh38

    jayh38 Active Member

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    You could use more ram and also look into why you are keeping all those processes open. Your httpd.conf may need a tweak with connection limits / keepalive etc etc among endless other possibilities.

    Hire someone to go through your system and give you a proper audit.
     

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