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Date: Fri, 11 Sep 2015 08:25:30 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: "William A. Mahaffey III" <wam@hiwaay.net>
cc: FreeBSD Questions !!!! <freebsd-questions@freebsd.org>
Subject: Re: followup storage question
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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.