From mboxrd@z Thu Jan 1 00:00:00 1970 From: david@lang.hm Subject: Re: [ANNOUNCE] Btrfs: a copy on write, snapshotting FS Date: Tue, 19 Jun 2007 11:24:30 -0700 (PDT) Message-ID: References: <20070612161029.GB28279@think.oraclecorp.com> <4676C2D6.8030708@vlnb.net> <46779DB1.7060807@draigBrady.com> <20070619120457.GD14108@think.oraclecorp.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: =?iso-8859-1?Q?P=E1draig?= Brady , Vladislav Bolkhovitin , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Chris Mason Return-path: Received: from dsl081-033-126.lax1.dsl.speakeasy.net ([64.81.33.126]:44185 "EHLO bifrost.lang.hm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757882AbXFSSYd (ORCPT ); Tue, 19 Jun 2007 14:24:33 -0400 In-Reply-To: <20070619120457.GD14108@think.oraclecorp.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Tue, 19 Jun 2007, Chris Mason wrote: >>> 3. De-de-duplicate blocks on disk, i.e. copy them on write >>> >>> I suppose that de-duplication itself would be done by some user space >>> process that would scan files, determine blocks with the same data and >>> then de-duplicate them by using syscall or IOCTL (2). >>> >>> That would be very usable feature, which in most cases would allow to >>> shrink occupied disk space on 50-90%. >> >> Have you references for this number? >> In my experience one gets a lot of benefit from >> the much simpler process of "de-duplication" of files. > > Yes, I would expect simple hard links to be a better solution for this, > but the feature request is not that out of line. I actually had plans > on implementing auto duplicate block reuse earlier in btrfs. with COW de-duplication you can merge things that have vastly different permissions. hard-links can't be used if different people have write permission. David Lang