How do I know if my disks are being hit with too much IO reads or writes or both?

Posted by Mark F on Server Fault See other posts from Server Fault or by Mark F
Published on 2011-01-09T22:38:36Z Indexed on 2011/01/09 22:55 UTC
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disk

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io

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iostat

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iowait

Hi All,

So I know a bit about disk I/O and bottlenecks relating to this especially when relating to databases.

But how do I really know what the max IO numbers will be for my disks? What metric might be available to me for working out roughly (but needs to be a good approximation) of how much capacity (if you will) have I got left available in I/O.

I've seen it before where things are bubbling along nicely and then all of a sudden, everything screams to a halt, and it ends up being an IO bound problem. Is there a better way to predict when IO is reaching its limits?

This article was interesting but not giving the answer I desire. "http://serverfault.com/questions/61510/linux-how-can-i-see-whats-waiting-for-disk-io". So is my best bet surrounding just looking at 'CPU IO WAIT'? There must be a more reactive method for this?

Best, M

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