From owner-freebsd-stable@FreeBSD.ORG  Tue Jul 15 15:06:50 2008
Return-Path: <owner-freebsd-stable@FreeBSD.ORG>
Delivered-To: freebsd-stable@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 61209106567E;
	Tue, 15 Jul 2008 15:06:50 +0000 (UTC)
	(envelope-from kris@FreeBSD.org)
Received: from weak.local (freefall.freebsd.org [IPv6:2001:4f8:fff6::28])
	by mx1.freebsd.org (Postfix) with ESMTP id D3D578FC16;
	Tue, 15 Jul 2008 15:06:48 +0000 (UTC)
	(envelope-from kris@FreeBSD.org)
Message-ID: <487CBD0A.6050207@FreeBSD.org>
Date: Tue, 15 Jul 2008 17:06:50 +0200
From: Kris Kennaway <kris@FreeBSD.org>
User-Agent: Thunderbird 2.0.0.14 (Macintosh/20080421)
MIME-Version: 1.0
To: Jeremy Chadwick <koitsu@FreeBSD.org>
References: <1216130834.27608.27.camel@lanshark.dmv.com>
	<20080715145426.GA31340@eos.sc1.parodius.com>
In-Reply-To: <20080715145426.GA31340@eos.sc1.parodius.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: Sven Willenberger <sven@dmv.com>, freebsd-stable@freebsd.org
Subject: Re: Multi-machine mirroring choices
X-BeenThere: freebsd-stable@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Production branch of FreeBSD source code <freebsd-stable.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>, 
	<mailto:freebsd-stable-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-stable>
List-Post: <mailto:freebsd-stable@freebsd.org>
List-Help: <mailto:freebsd-stable-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>,
	<mailto:freebsd-stable-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 15 Jul 2008 15:06:50 -0000

Jeremy Chadwick wrote:

> Compared to UFS2 snapshots (e.g. dump -L or mksnap_ffs), ZFS snapshots
> are fantastic.  The two main positives for me were:
> 
> 1) ZFS snapshots take significantly less time to create; I'm talking
> seconds or minutes vs. 30-45 minutes.  I also remember receiving mail
> from someone (on -hackers?  I can't remember -- let me know and I can
> dig through my mail archives for the specific mail/details) stating
> something along the lines of "over time, yes, UFS2 snapshots take
> longer and longer, it's a known design problem".
> 
> 2) ZFS snapshots, when created, do not cause the system to more or less
> deadlock until the snapshot is generated; you can continue to use the
> system during the time the snapshot is being generated.  While with
> UFS2, dump -L and mksnap_ffs will surely disappoint you.

"a known design problem" in the sense of "intentional", yes.  They were 
written to support bg fsck, not as a lightweight filesystem feature for 
general use.

Kris