Date: Tue, 8 May 2012 15:06:25 -0700 From: Artem Belevich <art@freebsd.org> To: Freddie Cash <fjwcash@gmail.com> Cc: freebsd-fs@freebsd.org, Michael Gmelin <freebsd@grem.de> Subject: Re: ZFS resilvering strangles IO Message-ID: <CAFqOu6hxww5a1CLwYOZZcZNkJVhwH2eUXmtJKNwm6ohNmcqP0Q@mail.gmail.com> In-Reply-To: <CAOjFWZ7ik_sUmUaw4im729dc-2Toq2j_z_oxiqUpzc4x_TOujQ@mail.gmail.com> 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> <CAOjFWZ7ik_sUmUaw4im729dc-2Toq2j_z_oxiqUpzc4x_TOujQ@mail.gmail.com>
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On Tue, May 8, 2012 at 2:33 PM, Freddie Cash <fjwcash@gmail.com> wrote: > 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. =A0Finding 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/syste= m: >> 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). =A0The default is 10. You may also want to look at vfs.zfs.scrub_limit sysctl. According to description it's "Maximum scrub/resilver I/O queue" which sounds like something that may help in this case. --Artem
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