More IO identification problems
Andriy Gapon
avg at freebsd.org
Fri Nov 26 13:41:15 UTC 2010
on 26/11/2010 08:05 Adam Vande More said the following:
> As a follow-up, after applying both patches presented in this thread(FreeBSD
> 8.2-PRERELEASE #5: Thu Nov 25 19:14:00 CST 2010),
>
> http://lists.freebsd.org/pipermail/freebsd-stable/2010-November/060298.html
>
> "top -m io" now displays much more info and is generally consistent with
> gstat in that IO spikes occer around the same time. However, gstat and "top
> -m io" are still not displaying any stats for 90%+ of my hard drive
> indicator light blinks. Since the issue effects gstat as well, it doesn't
> seem like it could be related to ZFS. When the system is basically idling,
> the only consistent IO related entries are these;
>
> 6 root 15 0 1 12 0 13 20.00%
> {l2arc_feed_threa}
> 6 root 15 0 1 12 0 13 20.00%
> {arc_reclaim_thre}
> 6 root 15 0 1 12 0 13 20.00% {zvol
> zoot/usr/ho}
> 6 root 15 0 1 12 0 13 20.00%
> {txg_thread_enter}
> 6 root 15 0 1 12 0 13 20.00%
> {txg_thread_enter}
>
> Entries like these occur like clockwork on 30 sec intervals. My theory here
> is that since the ZVOL has UFS + SU, this is causing a sync?
>
> What I'm trying to diagnose is a much more frequent hard drive access which
> occurs on approximately 2 sec intervals. I timed this by pinging localhost
> and comparing the response to the blinks. It's very consistent although not
> completely so as once in awhile the blink occurs every second. If I listen
> carefully I can hear increased drive activity during many of these intervals
> so the indicator light seems to be working correctly.
>
> If anyone has ideas or tests they'd like me to run, it would be appreciated.
>
Perhaps it's some external component?
E.g. hald is known to perform some disk/media checks every two seconds.
--
Andriy Gapon
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