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Date:      Thu, 14 Mar 2013 11:51:40 -0700
From:      Freddie Cash <fjwcash@gmail.com>
To:        Daniel Kalchev <daniel@digsys.bg>
Cc:        FreeBSD Filesystems <freebsd-fs@freebsd.org>
Subject:   Re: Strange slowdown when cache devices enabled in ZFS
Message-ID:  <CAOjFWZ718cGJUruysNYr%2BQuqX-RP2%2BdXAVTnMwnqFgz-%2BmkK9w@mail.gmail.com>
In-Reply-To: <26456299-66A3-4CCF-9B9A-906D47EFFC93@digsys.bg>
References:  <CAOjFWZ6Q=Vs3P-kfGysLzSbw4CnfrJkMEka4AqfSrQJFZDP_qw@mail.gmail.com> <26456299-66A3-4CCF-9B9A-906D47EFFC93@digsys.bg>

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I do have the following set in /boot/loader.conf:
vfs.zfs.l2arc_write_boost="160000000"           # Set the L2ARC warmup
writes to 160 MBps
vfs.zfs.l2arc_write_max="320000000"             # Set the L2ARC writes to
320 MBps

Haven't tried setting them any higher than that, though.

During the "0 I/O periods", there's no I/O going to the cache devices
either, and they're anywhere from 50% full to almost 100% full (as shown in
"zpool list -v" and "zpool iostat" output).  ARC use is close to max,
though.



On Thu, Mar 14, 2013 at 11:41 AM, Daniel Kalchev <daniel@digsys.bg> wrote:

> Just an idea - have you tried to increase the L2ARC fill rate? That might
> move data faster from RAM to L2ARC.. Don't remember the says to offhand.
>
> Might be dedup kicking in and not able to get "swapped out" fast enough.
>
> Daniel




-- 
Freddie Cash
fjwcash@gmail.com



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