From owner-freebsd-performance@FreeBSD.ORG  Thu Mar 22 21:31:34 2007
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From: Dieter <freebsd@sopwith.solgatos.com>
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Subject: Re: Slow on heavy I/O operations.
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> But what I can't understand - why such non-critical(as it seems to me)
> disk activity, cause 100% busyness for disk?

Others have pointed out the effect of seeking.

It would be very useful if there was a way to nice I/O up or down
the way we can nice CPU usage up or down.  Then non-critical
disk activity could be niced down and not impact critical I/O
so much.