From owner-freebsd-stable@FreeBSD.ORG  Fri May  1 20:53:12 2009
Return-Path: <owner-freebsd-stable@FreeBSD.ORG>
Delivered-To: freebsd-stable@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id CCFB61065795
	for <freebsd-stable@freebsd.org>; Fri,  1 May 2009 20:53:12 +0000 (UTC)
	(envelope-from petefrench@ticketswitch.com)
Received: from constantine.ticketswitch.com (constantine.ticketswitch.com
	[IPv6:2002:57e0:1d4e:1::3])
	by mx1.freebsd.org (Postfix) with ESMTP id 920968FC1B
	for <freebsd-stable@freebsd.org>; Fri,  1 May 2009 20:53:12 +0000 (UTC)
	(envelope-from petefrench@ticketswitch.com)
Received: from dilbert.rattatosk ([10.64.50.6] helo=dilbert.ticketswitch.com)
	by constantine.ticketswitch.com with esmtps (TLSv1:AES256-SHA:256)
	(Exim 4.69 (FreeBSD)) (envelope-from <petefrench@ticketswitch.com>)
	id 1LzzjJ-000GVh-6U; Fri, 01 May 2009 21:53:09 +0100
Received: from petefrench by dilbert.ticketswitch.com with local (Exim 4.69
	(FreeBSD)) (envelope-from <petefrench@ticketswitch.com>)
	id 1LzzjJ-0002eV-5A; Fri, 01 May 2009 21:53:09 +0100
To: freebsd-stable@freebsd.org, mike@sentex.net
In-Reply-To: <200905012041.n41Kf47B045440@lava.sentex.ca>
Message-Id: <E1LzzjJ-0002eV-5A@dilbert.ticketswitch.com>
From: Pete French <petefrench@ticketswitch.com>
Date: Fri, 01 May 2009 21:53:09 +0100
Cc: 
Subject: Re: current zfs tuning in RELENG_7 (AMD64) suggestions ?
X-BeenThere: freebsd-stable@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Production branch of FreeBSD source code <freebsd-stable.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>, 
	<mailto:freebsd-stable-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-stable>
List-Post: <mailto:freebsd-stable@freebsd.org>
List-Help: <mailto:freebsd-stable-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>,
	<mailto:freebsd-stable-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 01 May 2009 20:53:13 -0000

> In the past it had been suggested that for zfs tuning, something like
>
> vm.kmem_size_max="1073741824"
> vm.kmem_size="1073741824"
> vfs.zfs.prefetch_disable=1
>
> However doing a simple test with bonnie and dd, there does not seem 
> to be very much difference in 4 configs.  Am I better off just with 

The tuning isn't there to improve performance, it's there to prevent
the box going titus due to a panic when the ARC gets too big, and
you are missing the mian one, which is to limit the size of the ARC.
On recent versions of BSD (and you are running 7.2, so thats fine) then
the defaults for kmem size are fine, but you still need something like this:

vfs.zfs.arc_max="256M"

In there to stop the ARC growing. thats the only tuning I have on
my 4 gig machine, which takes a steady stream of data and is used
for taking backup snapshots. ZFS is excellent, and for me is perfectly
stable, to the point where I am starting to roll it out to production
machines, with the above tuning.

-pete.