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Date: Mon, 18 Mar 2013 11:50:21 -0400
From: Gary Palmer <gpalmer@freebsd.org>
To: Davide D'Amico <davide.damico@contactlab.com>
Subject: Re: FreBSD 9.1 and ZFS v28 performances
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On Mon, Mar 18, 2013 at 03:50:37PM +0100, Davide D'Amico wrote:
> Hi all,
> I'm trying to use ZFS on a DELL R720 with 2x6-core, 32GB ram, H710 
> controller (no JBOD) and 15K rpm SAS HD: I will use it for a mysql 5.6 
> server, so I am trying to use ZFS to get L2ARC and ZIL benefits.
> 
> I created a RAID10 and used zpool to create a pool on top:
> 
> # zpool create DATA mfid3
> # zpool add DATA cache mfid1 log mfid2
> 
> I have a question on zfs performances. Using:
> 
> dd if=/dev/zero of=file.out bs=16k count=1M
> 
> I cannot go faster than 400MB/s so I think I'm missing something; I 
> tried removing zil, removing l2arc but everything is still the same.
> 

If you have ufs on mfid3 then does the performance change?  How about
if you umount the filesystem and dd to the raw device?  In other words,
are you sure this is a zfs issue and not an issue somewhere else?
What I/O rate were you hoping/expecting to see?

Gary