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From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: "Bradley W. Dutton" <brad@duttonbros.com>
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Cc: freebsd-fs@freebsd.org
Subject: Re: ZFS performance of various vdevs (long post)
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On Mon, 7 Jun 2010, Bradley W. Dutton wrote:
>
> Are there any tools to check the latencies of the disks?

There might be something better, but 'iostat -x' is definitely your 
friend when it comes to looking at latencies under load.  Use a sample 
time of 30 seconds ('iostat -x 30').  Check if a few disks are much 
slower than the others.  If they are all about the same, then the 
disks are likely operating ok.  Sometimes it is found that one or two 
disks are abnormally slow, and this slows down the whole raidz.

Bob
-- 
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/