Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753279Ab1FHSuH (ORCPT ); Wed, 8 Jun 2011 14:50:07 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:31316 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753163Ab1FHSuB (ORCPT ); Wed, 8 Jun 2011 14:50:01 -0400 Message-ID: <4DEFC43B.1080802@oracle.com> Date: Wed, 08 Jun 2011 11:49:31 -0700 From: Sunil Mushran User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.17) Gecko/20110424 Lightning/1.0b2 Thunderbird/3.1.10 MIME-Version: 1.0 To: "Amir G." CC: Mike Snitzer , Lukas Czerner , linux-ext4@vger.kernel.org, tytso@mit.edu, linux-kernel@vger.kernel.org, sandeen@redhat.com Subject: Re: LVM vs. Ext4 snapshots (was: [PATCH v1 00/30] Ext4 snapshots) References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: rtcsinet22.oracle.com [66.248.204.30] X-CT-RefId: str=0001.0A090204.4DEFC44F.0174:SCFSTAT5015188,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 822 Lines: 16 On 06/08/2011 11:26 AM, Amir G. wrote: > 2. Data blocks are never copied > The move-on-write technique is used to re-allocate data blocks on rewrite > instead of copying them. > This is not something that can be done when the snapshot is stored on > external storage, but it can done when the snapshot file lives in the fs. But does that not lead to fragmentation. And if I am understanding this, the fragmentation will not resolve after dropping the snapshot. So while you do save the overhead on write, you make the user pay on all future reads (that need to hit the disk). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/