From owner-freebsd-fs@FreeBSD.ORG  Wed Jul  3 20:02:45 2013
Return-Path: <owner-freebsd-fs@FreeBSD.ORG>
Delivered-To: freebsd-fs@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by hub.freebsd.org (Postfix) with ESMTP id D005E80A
 for <freebsd-fs@freebsd.org>; Wed,  3 Jul 2013 20:02:45 +0000 (UTC)
 (envelope-from gpalmer@freebsd.org)
Received: from mail.in-addr.com (unknown [IPv6:2001:470:8:162::1])
 by mx1.freebsd.org (Postfix) with ESMTP id A4E4912BD
 for <freebsd-fs@freebsd.org>; Wed,  3 Jul 2013 20:02:45 +0000 (UTC)
Received: from gjp by mail.in-addr.com with local (Exim 4.80.1 (FreeBSD))
 (envelope-from <gpalmer@freebsd.org>)
 id 1UuTGD-000LwI-7Q; Wed, 03 Jul 2013 16:02:41 -0400
Date: Wed, 3 Jul 2013 16:02:41 -0400
From: Gary Palmer <gpalmer@freebsd.org>
To: Berend de Boer <berend@pobox.com>
Subject: Re: EBS snapshot backups from a FreeBSD zfs file system: zpool freeze?
Message-ID: <20130703200241.GB60515@in-addr.com>
References: <87li5o5tz2.wl%berend@pobox.com>
 <CA+tpaK1jQuKneQsxkVfxJGzXdPdLZfqBM1QWQ0e19nK5t71t1Q@mail.gmail.com>
 <87ehbg5raq.wl%berend@pobox.com>
 <20130703055047.GA54853@icarus.home.lan>
 <6488DECC-2455-4E92-B432-C39490D18484@dragondata.com>
 <CADBaqmihCB5JP01hLwXTWHoZiJJ5-jkT-Ro=oDwOcKZT_zvEKA@mail.gmail.com>
 <A5A66641-5EF9-454E-A767-009480EE404E@dragondata.com>
 <871u7g57rl.wl%berend@pobox.com>
 <op.wznad7th34t2sn@tech304.office.supranet.net>
 <87mwq34emp.wl%berend@pobox.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <87mwq34emp.wl%berend@pobox.com>
X-SA-Exim-Connect-IP: <locally generated>
X-SA-Exim-Mail-From: gpalmer@freebsd.org
X-SA-Exim-Scanned: No (on mail.in-addr.com); SAEximRunCond expanded to false
Cc: freebsd-fs <freebsd-fs@freebsd.org>
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Filesystems <freebsd-fs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/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, 03 Jul 2013 20:02:45 -0000

On Thu, Jul 04, 2013 at 07:39:26AM +1200, Berend de Boer wrote:
> Again, my request has *nothing* to do with EBS. If you have multiple
> disks in your pool, how can you make a backup you can restore from, at
> the hardware level.

Other than using SAN (FC or iSCSI), I know of no reason to do backups
at the raw disk level, nor any real demand.  

I've worked with people who have done LUN based backups in the past and
they have one drawback - they tend to back up the entire LUN, irrespective
of whether it is an allocated block or not.  Modern systems that implement
some kind of TRIM emulation (or cheat and sniff the filesystem block
allocation maps) may alleviate that problem.

However, in the vast majority of cases, people back up from above
the FS, not below.  This makes your use case probably more tied to EBS
than you may otherwise think.

Regards,

Gary