ZFS read/write performance slows with time
killing at multiplay.co.uk
Thu Mar 22 00:34:11 UTC 2012
----- Original Message -----
From: "andy thomas" <andy at time-domain.co.uk>
To: <freebsd-fs at freebsd.org>
Sent: Wednesday, March 21, 2012 11:56 PM
Subject: ZFS read/write performance slows with time
>A server running 64-bit FreeBSD 8.0 boots from a SATA disk and then mounts
> a ZFS mirror consisting of two SAS disks plus one spare. Immediately after
> booting, the filesystem is fast and responsive and 'zpool iostat -v tank'
> reports read and write disk bandwidths of over 22 MB.
> But over a period of time, this performance begins to deteriorate and
> after 180 days of uptime this server, which is running mail, samba and
> webmail servers in 3 separate jails, really struggles especially the IMAP
> daemon. zpool iostat -v reports a maximum read bandwidth of around 2MB and
> a write bandwidth of 143 KB maximum. Rebooting the system restores normal
> performance but the cycle gradually repeats itself.
> I can't see anything wrong in any log and the system has 12 GB of memory
> and a 2 Ghz quad-core Xeon CPU so it isn't under-resourced. At boot time
> ZFS reports its version as being 13 - could the problem be due to a memory
> leak or some other issue with early versions of ZFS that have since been
> fixed in later FreeBSD releases?
There are known issues with the code in 8.0 which could easily cause the
behaviour you describe, I'd recommend upgrading to 8-STABLE or 8.3-RELEASE
when its done as that brings in a large amount of fixes for ZFS including
v28 support iirc.
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