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Hello, several hours i have %wa value at around 20% probably because of script which backup virtual machines (vzdump) iotop (some writing goes up to the disk write limit (around ...
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  1. #1
    Linux User postcd's Avatar
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    Higher %wa value is not exactly same as i/o abusers?


    Hello,

    several hours i have %wa value at around 20%

    probably because of script which backup virtual machines (vzdump)

    iotop (some writing goes up to the disk write limit (around 45Mb/s)
    http://i.snag.gy/yjYRw.jpg

    i want to ask if you can advice me any more command tools to track the exact cause of high %wa
    "Avoid the Gates of Hell. Use Linux affordable VPS."

  2. #2
    Linux Guru Rubberman's Avatar
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    See my reply to your other message. We need full information from you: host OS, guest OS's, disc information, controller information, file systems used, host system hardware information... More is better if you want real help.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  3. #3
    Linux User postcd's Avatar
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    Quote Originally Posted by Rubberman View Post
    See my reply to your other message. We need full information from you: host OS, guest OS's, disc information, controller information, file systems used, host system hardware information... More is better if you want real help.
    is there any command set which output these data?
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    Linux Guru Rubberman's Avatar
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    Look into the sar command. It is part of the sysstat services. Here are the contents to /etc/cron.d/sysstat:
    Code:
    # Run system activity accounting tool every 10 minutes
    */10 * * * * root /usr/lib64/sa/sa1 1 1
    # 0 * * * * root /usr/lib64/sa/sa1 600 6 &
    # Generate a daily summary of process accounting at 23:53
    53 23 * * * root /usr/lib64/sa/sa2 -A
    Note that it is run every 10 minutes. I usually change that to 1 minute intervals for production systems, then push the data into a hadoop time-series database so I can nicely graph out the performance of the system over time. You probably want to add the -A option so it gets network, disc I/O, and lots of other good stuff.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  6. #5
    Linux Engineer docbop's Avatar
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    Quote Originally Posted by postcd View Post

    i want to ask if you can advice me any more command tools to track the exact cause of high %wa
    You have to be careful all these tracking tools are a Catch-22 because they chew up a lot resources themselves.
    A lion does not lose sleep, over the opinion of sheep.

  7. #6
    Linux Guru Rubberman's Avatar
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    I haven't seen that (chewing up a lot of system resources) with the sysstat (sar) tools. We run them on heavily loaded systems and they are almost invisible when running. Primarily, sar sucks data out of /proc and then formats it for further analysis, storing the data in /var/log/sa in binary and ascii (printable) format. We also stream it continuously on 60 second intervals to store in an external hadoop or redshift cluster in the Amazon cloud. We store billions of data points per day, and our data collection tools to do so take much less than 1% of a single core for each server and since they are written in C++, the memory foot print is under 100 kilobytes.

    FWIW, this is what I do for a living - senior performance engineer for Nokia Mobile Phones, now part of Microsoft Devices.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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