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 iAJHJtr22617 for ; Fri, 19 Nov 2004 12:19:55 -0500 Received: from mail.rnbhq.org (foobar@preston.muon.de [82.165.25.30]) by mx1.redhat.com (8.12.11/8.12.11) with ESMTP id iAJHJojr021623 for ; Fri, 19 Nov 2004 12:19:51 -0500 Received: from port-212-202-8-76.dynamic.qsc.de ([212.202.8.76] helo=sisko.muon.local ident=foobar) by mail.rnbhq.org with asmtp (Cipher TLSv1:DES-CBC3-SHA:168) (Exim 3.35 #1 (Debian)) id 1CVCQ2-0000cw-00 for ; Fri, 19 Nov 2004 18:19:34 +0100 Received: from trip.muon.local ([192.168.0.248] helo=trip ident=Debian-exim) by sisko.muon.local with esmtp (Exim 3.35 #1 (Debian)) id 1CVCQ1-0000dL-00 for ; Fri, 19 Nov 2004 18:19:33 +0100 Received: from juergens by trip with local (Exim 4.34) id 1CVCQ1-0000Q1-8G for linux-lvm@redhat.com; Fri, 19 Nov 2004 18:19:33 +0100 Date: Fri, 19 Nov 2004 18:19:33 +0100 From: Nils Juergens Subject: Re: [linux-lvm] relocate on write for snapshot Message-ID: <20041119171933.GA1417@trip.muon.local> References: <1100882347.2984.32.camel@localhost.localdomain> Mime-Version: 1.0 Content-Disposition: inline In-Reply-To: <1100882347.2984.32.camel@localhost.localdomain> Sender: Debian User Reply-To: 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" Content-Transfer-Encoding: 7bit To: linux-lvm@redhat.com On Fri, 19.11.04, Ming Zhang wrote: > instead of copy old one to snapshot, overwrite old one with new one, 2 > writes and 1 reads. it is possible that write new data to a usused > location directly. Since you have to delete the snapshot (and I don't think they live very long on most systems) you don't gain anything (because you have copy the changes back from the snapshot), but you make the cases of more than one snapshot and (possibly) read-write snapshots a lot harder, maybe not in CPU or IO, but certainly in code complexity, which is a thing you never do to gain a bit of performance. > i know later remove a snaphot will be a little trouble, but there must > be some way to get around it. Yes, you have to do the work you saved a couple of minutes earlier :) just my EUR 0.02, Nils -- Nils Juergens | nils@muon.de | icq 7090774 Having problems sending big files over the net? Try out Efisto (http://efisto.org).