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From: Artem Belevich <art@freebsd.org>
To: Robert Schulze <rs@bytecamp.net>
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Cc: freebsd-fs@freebsd.org
Subject: Re: zfs l2arc issue
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On Thu, May 5, 2011 at 1:19 AM, Robert Schulze <rs@bytecamp.net> wrote:
> All drives except the caching SSDs are attached to a LSI 9690SA-8I.
> The system is equipped with 32 GB RAM, and runs with a load of <1, please
> note: we are running 8.0, yet, since there was one issue with ZFS which
> blocked the upgrade to 8-STABLE.
>
> After about 100d uptime, we had a sudden large increase in load of about
> 5-7, nfsd had 100-400% WCPU. Also an rsync downloading files from that
> machine was very slow.

There was an issue with clock_t type overflow . It was fixed in
r218429 on Feb 8th in 8-stable.
One of its effects was that it would cause L2ARC feeding thread to
spin endlessly after about a month of uptime. It's possible that there
are other scenarios where clock_t overflow in ZFS code would cause
strange things to happen. I would suggest migrating to 8-STABLE as
there were number of ZFS-related fixes committed since 8.0.

--Artem