What is 'steal time' in my sysstat output?

After running sar on my new slice from SliceHost*, I noticed a new column called steal. It's generally very low on my virtual machine, and I've never seen it creep over 1-2%.

IBM's definition of steal time is actually pretty good:

Steal time is the percentage of time a virtual CPU waits for a real CPU while the hypervisor is servicing another virtual processor.

So, relatively speaking, what does this mean?

A high steal percentage may mean that you may be outgrowing your virtual machine with your hosting company. Other virtual machines may have a larger slice of the CPU's time and you may need to ask for an upgrade in order to compete. Also, a high steal percentage may mean that your hosting company is overselling virtual machines on your particular server. If you upgrade your virtual machine and your steal percentage doesn't drop, you may want to seek another provider.

A low steal percentage can mean that your applications are working well with your current virtual machine. Since your VM is not wrestling with other VM's constantly for CPU time, your VM will be more responsive. This may also suggest that your hosting provider is underselling their servers, which is definitely a good thing.

* I've been a customer of SliceHost for a while (prior to Rackspace's acquisition), and I recommend them to anyone who needs a solid VM solution. If you want to help out with my hosting costs, you're welcome to use my SliceHost referral link.

Printed from: http://rackerhacker.com/2008/11/04/what-is-steal-time-in-my-sysstat-output/ .
© Major Hayden 2012.

3 Comments   »

  • Big D says:

    I love you major...

  • MKP says:

    One question Major, if I have a machine with actualization, and only one account, would it cause it to have some %age of steal time?

    --Mkp

  • matiu says:

    MKP, I think generally DOM0 (the host OS) will be able to steal time from the DOM1.

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  • Welcome! I started this blog as a way to give back to all of the other system administrators who have taught me something in the past. Writing these posts brings me a lot of enjoyment and I hope you find the information useful. If you spot something that's incorrect or confusing, please write a comment and let me know. Drop me a line if there's something you want to know more about and I'll do my best to write a post on the topic.
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