very slow zfs scrub

[Piotr Kucharski]

I was checking on it infrequently and now, almost 3 years later, it seems
to have been fixed. :)

Scrub in progress for 50h, 6.86T scanned out of 11.6T at 40M/s, 34h43m to
go, 0 repaired, 59.18% done.

Each 0.01T varies in speed, from 5M/s (fortunately, very rare) to 85M/s,
but average of 40M/s is good enough to let it finish (for the first time in
this filesystem history! :>)

I did not change hardware nor ggate setup, "only" FreeBSD got upgraded, now
it is FreeBSD 9.1-STABLE #75 r251912 with no patches.

Just informing so it does not scare people if they stumble upon this
thread. :)


On 19 May 2011 18:29, Piotr Kucharski <piotr.kucharski at 42.pl> wrote:

> On Thu, Feb 24, 2011 at 21:00, Adam Vande More <amvandemore at gmail.com>
> wrote:
> >> Wow! What does scrub do that it slows ggate drive almost to halt?
> >>
> >> What can I do to fix it?
> >
> > I think network latency is going to have huge impact on performance here.
> > Have you tried any ggate or nic tuning?  Would HAST be an option for
> you?  I
> > think it has more performance thought put into it.
> >
>
> Well, the network seems rather idle, host and client share the same
> 1Gb LAN (not sure if the same switch, though) with <0.2ms rtt for 1k
> packets in ping. When not scrubbing, sequential reads are
> satisfactory. I'm inclined to think some read or write pattern of
> scrub that is causing ggate to suck immensely. :/
>