From owner-freebsd-fs@FreeBSD.ORG  Sat Sep 17 17:54:38 2011
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From: "David P. Discher" <dpd@bitgravity.com>
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Date: Sat, 17 Sep 2011 10:54:34 -0700
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To: Lytochkin Boris <lytboris@gmail.com>
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Cc: freebsd-fs@freebsd.org
Subject: Re: [ZFS] starving reads while idle disks
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Do you see the same read-stravation when writing the tar to a file ? =
(possibly outside the zpool).

I have anecdotal suspicion that /dev/null has some performance hit of =
blocking or locking.=20

-dpd


On Sep 17, 2011, at 5:02 AM, Lytochkin Boris wrote:

> While runnig `tar cf - . >/dev/null', `vmstat -i' shows ~200
> interrupts per second for mpt. If I enable scrub on that pool,
> interrupts bump upto 5k ips resulting 12Mb/s scrub speed and disks
> busy percentage raises upto 100%. No warnings are shown in logs in
> both cases.