From owner-freebsd-stable@FreeBSD.ORG Thu Jul 22 10:24:37 2010 Return-Path: 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 C84EF106567D for ; Thu, 22 Jul 2010 10:24:37 +0000 (UTC) (envelope-from doconnor@gsoft.com.au) Received: from cain.gsoft.com.au (cain.gsoft.com.au [203.31.81.10]) by mx1.freebsd.org (Postfix) with ESMTP id 2FE068FC12 for ; Thu, 22 Jul 2010 10:24:36 +0000 (UTC) Received: from ur.dons.net.au (ppp121-45-158-44.lns6.adl6.internode.on.net [121.45.158.44]) (authenticated bits=0) by cain.gsoft.com.au (8.14.4/8.14.3) with ESMTP id o6MAOMLc042265 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Thu, 22 Jul 2010 19:54:28 +0930 (CST) (envelope-from doconnor@gsoft.com.au) Mime-Version: 1.0 (Apple Message framework v1081) Content-Type: text/plain; charset=us-ascii From: "Daniel O'Connor" In-Reply-To: Date: Thu, 22 Jul 2010 19:54:22 +0930 Content-Transfer-Encoding: quoted-printable Message-Id: <5609C94D-CDD7-4798-9E60-7686086999A1@gsoft.com.au> References: <4C47B57F.5020309@langille.org> To: Adam Vande More X-Mailer: Apple Mail (2.1081) X-Spam-Score: 0.163 () BAYES_00,RDNS_DYNAMIC X-Scanned-By: MIMEDefang 2.67 on 203.31.81.10 Cc: Charles Sprickman , freebsd-stable , Dan Langille Subject: Re: Using GTP and glabel for ZFS arrays X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 22 Jul 2010 10:24:37 -0000 On 22/07/2010, at 13:59, Adam Vande More wrote: > To be clear, we are talking about data partitions, not the boot one. > Difficult for me to explain concisely, but basically it has to do with = seek > time. A mis-aligned partition will almost always have an extra seek = for > each standard seek you'd have on aligned one. There have been some > discussions about in the archives, also this is not unique to FreeBSD = so > google will have a more detailed and probably better explanation. Newer disks have 4kb sectors internally at least, and some expose it to = the OS. If you create your partitions unaligned to this every read and write = will involve at least one more sector than it would otherwise and that = hurts performance. The disks which don't expose it have a jumper which offsets all accesses = to Windows XP's performance doesn't take a dive but I'm not sure if that = helps FreeBSD. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C