From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id k11NMT116016 for ; Wed, 1 Feb 2006 18:22:29 -0500 Received: from orca.ele.uri.edu (orca.ele.uri.edu [131.128.51.63]) by mx1.redhat.com (8.12.11/8.12.11) with ESMTP id k11NMSA0008860 for ; Wed, 1 Feb 2006 18:22:28 -0500 Subject: Re: [linux-lvm] 'snapshot' target still experimental :-( From: Ming Zhang In-Reply-To: <1138830708.15727.20.camel@pc.ilinx> References: <43E0E3E3.3030407@starnetworks.us> <1138829354.26648.85.camel@seki.nac.uci.edu> <1138830708.15727.20.camel@pc.ilinx> Date: Wed, 01 Feb 2006 18:22:09 -0500 Message-Id: <1138836130.4762.146.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Reply-To: mingz@ele.uri.edu, LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii" To: LVM general discussion and development On Wed, 2006-02-01 at 16:51 -0500, Brian J. Murrell wrote: > On Wed, 2006-02-01 at 13:29 -0800, Dan Stromberg wrote: > > It just maintains a series of hardlink trees, so any time a file is > > deleted or added, the actual disk usage increase is only due to the > > changes. > > Yes, this is quite a popular technique. To be clear though, a change in > a file does not consume just the amount of the change in the file on the > backup target, but it consumes the entire size of the new file. A > not-so-insignificant amount for very large files. This is where a > (block level or filesystem level) snapshotting scheme would excel as it > would likely only consume an amount of space rounded up to the next > "unit" size more even for changes within a file. it depends. assume u have a huge text file. u change 1 char, the snapshot is useful. u add one line at the beginning, the snapshot is useless here. the offset shift. some delta tech will be useful here. > > Indeed (and to keep quite on topic), perhaps rather than hardlink trees, > LVM snapshots would be even more space efficient. Maybe that is what > this thread has been about. I just jumped in. Apologies if it was. > > b. > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/