From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263122AbTJPVZW (ORCPT ); Thu, 16 Oct 2003 17:25:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263130AbTJPVZW (ORCPT ); Thu, 16 Oct 2003 17:25:22 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:22992 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S263122AbTJPVZU (ORCPT ); Thu, 16 Oct 2003 17:25:20 -0400 Message-ID: <3F8F0CB2.7050002@pobox.com> Date: Thu, 16 Oct 2003 17:25:06 -0400 From: Jeff Garzik User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030703 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Chris Meadors CC: Linux Kernel Subject: Re: Transparent compression in the FS References: <1066163449.4286.4.camel@Borogove> <20031015133305.GF24799@bitwizard.nl> <3F8D6417.8050409@pobox.com> <20031016162926.GF1663@velociraptor.random> <20031016172930.GA5653@work.bitmover.com> <20031016174927.GB25836@speare5-1-14> <3F8F0766.30405@pobox.com> <1066339127.3958.8.camel@clubneon.priv.hereintown.net> In-Reply-To: <1066339127.3958.8.camel@clubneon.priv.hereintown.net> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Chris Meadors wrote: > On Thu, 2003-10-16 at 17:02, Jeff Garzik wrote: > > >>I'm curious if anyone has done any work on using multiple different >>checksums? For example, the cost of checksumming a single block with >>multiple algorithms (sha1+md5+crc32 for a crazy example), and storing >>each checksum (instead of just one sha1 sum), may be faster than reading >>the block off of disk to compare it with the incoming block. OTOH, >>there is still a mathematical possibility (however-more-remote) of a >>collission... > > > I don't think multiple hashes will gain any more uniqueness over just a > larger hash value. I disagree... But as long as the hash is smaller than the block > being hashed there is the possibility of two dissimilar blocks producing > the same hash. Agreed. Jeff