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Date:      Tue, 8 May 2012 14:33:23 -0700
From:      Freddie Cash <fjwcash@gmail.com>
To:        Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
Cc:        freebsd-fs@freebsd.org, Michael Gmelin <freebsd@grem.de>
Subject:   Re: ZFS resilvering strangles IO
Message-ID:  <CAOjFWZ7ik_sUmUaw4im729dc-2Toq2j_z_oxiqUpzc4x_TOujQ@mail.gmail.com>
In-Reply-To: <alpine.GSO.2.01.1205081625470.9406@freddy.simplesystems.org>
References:  <73F8D020-04F3-44B2-97D4-F08E3B253C32@grem.de> <CAFHbX1K0--P-Sh0QdLszEs0V1ocWoe6Jp_SY9H%2BVJd1AQw2XKA@mail.gmail.com> <180B72CE-B285-4702-B16D-0714AA07022C@grem.de> <alpine.GSO.2.01.1205081625470.9406@freddy.simplesystems.org>

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On Tue, May 8, 2012 at 2:31 PM, Bob Friesenhahn
<bfriesen@simple.dallas.tx.us> wrote:
> On Tue, 8 May 2012, Michael Gmelin wrote:
>>
>> Do you think it would make sense to try to play with zfs_resilver_delay
>> directly in the ZFS kernel module?
>
> This may be the wrong approach if the issue is really that there are too
> many I/Os queued for the device. =C2=A0Finding a tunable which reduces th=
e
> maximum number of I/Os queued for a disk device may help reduce write
> latencies by limiting the backlog.
>
> On my Solaris 10 system, I accomplished this via a tunable in /etc/system=
:
> set zfs:zfs_vdev_max_pending =3D 5
>
> What is the equivalent for FreeBSD?

Setting vfs.zfs.vdev_max_pending=3D"4" in /boot/loader.conf (or whatever
value you want).  The default is 10.

> Bob
> --
> Bob Friesenhahn
> bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen=
/
> GraphicsMagick Maintainer, =C2=A0 =C2=A0http://www.GraphicsMagick.org/
> _______________________________________________
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--=20
Freddie Cash
fjwcash@gmail.com



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