From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753154AbYI1CR4 (ORCPT ); Sat, 27 Sep 2008 22:17:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751923AbYI1CRs (ORCPT ); Sat, 27 Sep 2008 22:17:48 -0400 Received: from www.church-of-our-saviour.org ([69.25.196.31]:57962 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751684AbYI1CRs (ORCPT ); Sat, 27 Sep 2008 22:17:48 -0400 Date: Sat, 27 Sep 2008 22:17:46 -0400 From: Theodore Tso To: Ivan Zorin Cc: linux-kernel@vger.kernel.org Subject: Re: [question] "copy-on-write" in ext4 Message-ID: <20080928021746.GB5025@mit.edu> Mail-Followup-To: Theodore Tso , Ivan Zorin , linux-kernel@vger.kernel.org References: <48DEBCE9.3000002@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48DEBCE9.3000002@gmail.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@mit.edu X-SA-Exim-Scanned: No (on thunker.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 28, 2008 at 03:08:25AM +0400, Ivan Zorin wrote: > Hello, everybody. I have a question to ext4 filesystem developers. Could > you tell me please, have you planned to implement (no matter, how soon) > in ext4 some "copy-on-write" feature? If you have, then how it will be > looks like (and how soon :-) ? > If you haven't, then did you think about ability to implement such > feature and how it could be? What do you mean by "copy on write", precisely? Do you mean at the file level, directory level, or the filesystem level? We don't have any plans to implement "copy on write" in ext4, although you can create a copy-on-write snapshot at the block device level using LVM/devicemapper. For many things (database backups, etc.) this is quite suitable. So why don't you tell us what you are trying to do, and we can suggest to you ways that you might be able to do it. - Ted