ZFS resilvering strangles IO

[Freddie Cash]

On Tue, May 8, 2012 at 2:31 PM, Bob Friesenhahn
<bfriesen at 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.  Finding a tunable which reduces the
> 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 = 5
>
> What is the equivalent for FreeBSD?

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

> Bob
> --
> Bob Friesenhahn
> bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
> GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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-- 
Freddie Cash
fjwcash at gmail.com