From owner-freebsd-current@FreeBSD.ORG Tue Oct 8 20:41:35 2013 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id E3C91219 for ; Tue, 8 Oct 2013 20:41:35 +0000 (UTC) (envelope-from nwhitehorn@freebsd.org) Received: from smtpauth3.wiscmail.wisc.edu (wmauth3.doit.wisc.edu [144.92.197.226]) (using TLSv1 with cipher RC4-MD5 (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 9BC8F2F8A for ; Tue, 8 Oct 2013 20:41:35 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 8BIT Content-type: text/plain; charset=UTF-8 Received: from avs-daemon.smtpauth3.wiscmail.wisc.edu by smtpauth3.wiscmail.wisc.edu (Oracle Communications Messaging Server 7u4-27.01(7.0.4.27.0) 64bit (built Aug 30 2012)) id <0MUD00I00A0CAR00@smtpauth3.wiscmail.wisc.edu> for freebsd-current@freebsd.org; Tue, 08 Oct 2013 15:41:34 -0500 (CDT) X-Spam-PmxInfo: Server=avs-3, Version=6.0.3.2322014, Antispam-Engine: 2.7.2.2107409, Antispam-Data: 2013.10.8.203040, SenderIP=0.0.0.0 X-Spam-Report: AuthenticatedSender=yes, SenderIP=0.0.0.0 Received: from wanderer.tachypleus.net (unknown [140.105.20.242]) by smtpauth3.wiscmail.wisc.edu (Oracle Communications Messaging Server 7u4-27.01(7.0.4.27.0) 64bit (built Aug 30 2012)) with ESMTPSA id <0MUD006DEAT6UX40@smtpauth3.wiscmail.wisc.edu>; Tue, 08 Oct 2013 15:41:32 -0500 (CDT) Message-id: <52546DFA.4000500@freebsd.org> Date: Tue, 08 Oct 2013 22:41:30 +0200 From: Nathan Whitehorn User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:24.0) Gecko/20100101 Thunderbird/24.0 To: Freddie Cash Subject: Re: [CFT] Patch to bsdinstall to support root-on-ZFS and GELI References: <52531295.7090700@allanjude.com> <52546844.2010608@freebsd.org> In-reply-to: X-Enigmail-Version: 1.5.2 Cc: FreeBSD-Current , Allan Jude X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Oct 2013 20:41:36 -0000 On 10/08/13 22:25, Freddie Cash wrote: > On Tue, Oct 8, 2013 at 1:17 PM, Nathan Whitehorn > >wrote: > > 4. What is this gnop stuff for? > > > Can't comment on the rest, but gnop is required to create 4K-aligned > vdevs where the minimum block size is 4K (aka ashift=12). Without > this, ZFS relies on the underlying disk driver providing the correct > information, and most don't. Also, if you don't do this, and create a > vdev using 512B sectors, the ashift will be set to 9, and replacing > the drive down the line with 4K Advanced Format drive will drop your > drive performance in the toilet.​​ > > Thus, to future-proof your pool, you need to: > - set the ashift of the pool to 12 (4 KB) > - align the disk/partition on 4 KB boundaries (starting partition at > 1 MB works well) > > Until our ZFS gains the ability to set a minimum ashift for the pool, > or to set the ashift at vdev creation, or all drive manufacturers > write perfect firmware, than we need to fake it with gnop. > Well, that's a disgusting hack, but I see why it's there. Thanks for the explanation! -Nathan