How do I know if my disks are being hit with too many I/O 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 2011/01/10 1:55 UTC
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disk

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io

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throughput

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iostat

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iowait

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

How do I really know what the max I/O 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 I/O bound problem. Is there a better way to predict when I/O is reaching its limits?

This article was interesting but not giving the answer I desire. So, is my best bet surrounding just looking at 'CPU I/O WAIT'? There must be a more reactive method than this.

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