From: Christoph Hellwig Subject: Re: LVM vs. Ext4 snapshots (was: [PATCH v1 00/30] Ext4 snapshots) Date: Thu, 9 Jun 2011 06:52:20 -0400 Message-ID: <20110609105220.GA3300@infradead.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mike Snitzer , Lukas Czerner , linux-ext4@vger.kernel.org, tytso@mit.edu, linux-kernel@vger.kernel.org, sandeen@redhat.com To: "Amir G." Return-path: Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:56725 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754720Ab1FIKw0 (ORCPT ); Thu, 9 Jun 2011 06:52:26 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Jun 08, 2011 at 09:26:11PM +0300, Amir G. wrote: > In my old next3.sf.net wiki, which I do update from time to time, > I listed 4 advantages of Ext4 (then next3) snapshots over LVM: > * Performance: only small overhead to write performance with snapshots > * Scalability: no extra overhead per snapshot > * Maintenance: no need to pre-allocate disk space for snapshots > * Persistence: snapshots don't vanish when disk is full > > As far as I know, the only thing that has changed from dm-snap > to dm-multisnap is the Scalability. I don't think you have looked at dm-multisnap at all, have you? It addresses all your points and many more. Take a look at the code which is in the multisnap branch of https://github.com/jthornber/linux-2.6/, there's also some slides on it from Linuxtag at: https://github.com/jthornber/storage-papers/blob/master/thinp-snapshots-2011/thinp-and-multisnap.otp?raw=true