From owner-freebsd-questions@freebsd.org  Fri Sep 11 15:03:37 2015
Return-Path: <owner-freebsd-questions@freebsd.org>
Delivered-To: freebsd-questions@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id 7A9A6A01F5E
 for <freebsd-questions@mailman.ysv.freebsd.org>;
 Fri, 11 Sep 2015 15:03:37 +0000 (UTC) (envelope-from wam@hiwaay.net)
Received: from fly.hiwaay.net (fly.hiwaay.net [216.180.54.1])
 (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 4BE54117E
 for <freebsd-questions@freebsd.org>; Fri, 11 Sep 2015 15:03:36 +0000 (UTC)
 (envelope-from wam@hiwaay.net)
Received: from kabini1.local (dynamic-216-186-222-143.knology.net
 [216.186.222.143] (may be forged)) (authenticated bits=0)
 by fly.hiwaay.net (8.13.8/8.13.8/fly) with ESMTP id t8BF3YOe007788
 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO)
 for <freebsd-questions@freebsd.org>; Fri, 11 Sep 2015 10:03:35 -0500
Subject: Re: followup storage question
References: <55F2D086.6060509@hiwaay.net>
 <alpine.BSF.2.20.1509110821560.6365@wonkity.com>
Cc: FreeBSD Questions !!!! <freebsd-questions@freebsd.org>
From: "William A. Mahaffey III" <wam@hiwaay.net>
Message-ID: <55F2ED46.6060708@hiwaay.net>
Date: Fri, 11 Sep 2015 10:09:04 -0453.75
User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:38.0) Gecko/20100101
 Thunderbird/38.2.0
MIME-Version: 1.0
In-Reply-To: <alpine.BSF.2.20.1509110821560.6365@wonkity.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions/>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 11 Sep 2015 15:03:37 -0000

On 09/11/15 09:31, Warren Block wrote:
> On Fri, 11 Sep 2015, William A. Mahaffey III wrote:
>
>> The Wiki page 
>> https://wiki.freebsd.org/RootOnZFS/GPTZFSBoot/9.0-RELEASE illustrates 
>> using gnop to enforce 4K alignment of gpt partitions for subsequent 
>> use by ZFS. However the gpart commands also use the '-a 4k' 
>> arguments, aligning partitions on 4k boundaries as I understand 
>> things. Is the gnop command also necessary ? TIA & have a nice weekend.
>
> These are two separate things.  gnop(8) is (was) used to force ZFS to 
> use a 4K block size.  That just means it transfers data in multiples 
> of 4K, not necessarily aligned with the 4K sectors on the drive. 
> gpart(8)'s -a flag is used to force partitions to begin in alignment 
> with the 4K sectors on the drive.
>

Hmmmm .... OK, however if I carefully 'gpart -a 4k' the underlying 
partitions aligned, then wouldn't the resulting ZFS above also be 
aligned ? I ask because the 2nd system I will be setting up in the next 
few weeks will probably use a RAIDZ1 on 6-8 partitions, & I have it on 
pretty good authority that you want RAID5-type storage properly aligned 
on the underlying drives or partitions. Thanks & TIA & have a nice weekend.

-- 

	William A. Mahaffey III

  ----------------------------------------------------------------------

	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                            -- Gen. George S. Patton Jr.