From owner-freebsd-fs@FreeBSD.ORG  Wed Mar  2 23:28:08 2011
Return-Path: <owner-freebsd-fs@FreeBSD.ORG>
Delivered-To: freebsd-fs@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id AA5931065676
	for <freebsd-fs@freebsd.org>; Wed,  2 Mar 2011 23:28:08 +0000 (UTC)
	(envelope-from james-freebsd-fs2@jrv.org)
Received: from mail.jrv.org (rrcs-24-73-246-106.sw.biz.rr.com [24.73.246.106])
	by mx1.freebsd.org (Postfix) with ESMTP id 6B58B8FC15
	for <freebsd-fs@freebsd.org>; Wed,  2 Mar 2011 23:28:08 +0000 (UTC)
Received: from kremvax.housenet.jrv (kremvax.housenet.jrv [192.168.3.124])
	by mail.jrv.org (8.14.4/8.14.4) with ESMTP id p22NS5uG089971;
	Wed, 2 Mar 2011 17:28:07 -0600 (CST)
	(envelope-from james-freebsd-fs2@jrv.org)
Authentication-Results: mail.jrv.org; domainkeys=pass (testing)
	header.from=james-freebsd-fs2@jrv.org
DomainKey-Signature: a=rsa-sha1; s=enigma; d=jrv.org; c=nofws; q=dns;
	h=message-id:date:from:user-agent:mime-version:to:cc:subject:
	references:in-reply-to:content-type:content-transfer-encoding;
	b=vKQT+efpa2KltR/y0Zu+58Fl8Msyz3IkQuBdtWfYCrxYTCLJ5LpFyYxHvhPSXRxym
	CdbhhsTCHZned/NUZIfkFpCgkq8+mPv0NhcSgB3FxIdi4H97Jzj6ZCYkM1wtJLHTImt
	Ik/6QFzbGe6sd0mBBTio5CHf+wLAiWqPavrbMwk=
Message-ID: <4D6ED285.6010105@jrv.org>
Date: Wed, 02 Mar 2011 17:28:05 -0600
From: "James R. Van Artsdalen" <james-freebsd-fs2@jrv.org>
User-Agent: Thunderbird 2.0.0.24 (Macintosh/20100228)
MIME-Version: 1.0
To: Emil Smolenski <am@raisa.eu.org>
References: <op.vn2iid1qk84lxj@arrow>
	<4D6AAC9A.4000602@jrv.org>	<op.vrmp2hrck84lxj@bolt.zol>	<AANLkTi=w9_d=2W_-_F62AxenmdBs7rE+bVAbmR2e877y@mail.gmail.com>
	<op.vrm32cqdk84lxj@bolt.zol>
In-Reply-To: <op.vrm32cqdk84lxj@bolt.zol>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Cc: freebsd-fs@freebsd.org
Subject: Re: [ZFS] Booting from zpool created on 4k-sector drive
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Filesystems <freebsd-fs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
	<mailto:freebsd-fs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-fs>
List-Post: <mailto:freebsd-fs@freebsd.org>
List-Help: <mailto:freebsd-fs-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
	<mailto:freebsd-fs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 02 Mar 2011 23:28:08 -0000

Emil Smolenski wrote:
> James asks about disk replacement scenario. In this case you cannot
> use device with greater sector size than 2**ashift of the existing
> vdev as replacement:
>
> # diskinfo -v md0 |grep sectorsize
>         512             # sectorsize
> # zpool create test0 md0
> # zdb test0 |grep ashift
>                 ashift=9
> # diskinfo -v md1.nop |grep sectorsize
>         4096            # sectorsize
> # zpool replace test0 md0 md1.nop
> cannot replace md0 with md1.nop: devices have different sector alignment

I was thinking of the capacity of the drive as a problem, not the sector
sizes.  I wrongly thought gnop consumed space on the drive (like
gmirror) and this might make it hard to replace an ashift=12 disk with a
512-byte-sector disk.  But this is not the case.

It might be a good idea now to start using the gnop trick to force
vdev's to use ashift=12 in case disks begin advertising themselvess as
4096-byte-sector.