Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754952AbWL1T7Y (ORCPT ); Thu, 28 Dec 2006 14:59:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754954AbWL1T7Y (ORCPT ); Thu, 28 Dec 2006 14:59:24 -0500 Received: from mail-gw1.sa.eol.hu ([212.108.200.67]:51819 "EHLO mail-gw1.sa.eol.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754951AbWL1T7X (ORCPT ); Thu, 28 Dec 2006 14:59:23 -0500 To: bhalevy@panasas.com CC: arjan@infradead.org, mikulas@artax.karlin.mff.cuni.cz, jaharkes@cs.cmu.edu, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, nfsv4@ietf.org In-reply-to: <4593E1B7.6080408@panasas.com> (message from Benny Halevy on Thu, 28 Dec 2006 17:24:39 +0200) Subject: Re: Finding hardlinks References: <20061221185850.GA16807@delft.aura.cs.cmu.edu> <1166869106.3281.587.camel@laptopd505.fenrus.org> <4593890C.8030207@panasas.com> <1167300352.3281.4183.camel@laptopd505.fenrus.org> <4593E1B7.6080408@panasas.com> Message-Id: From: Miklos Szeredi Date: Thu, 28 Dec 2006 20:58:38 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1219 Lines: 31 > >> It seems like the posix idea of unique doesn't > >> hold water for modern file systems > > > > are you really sure? > > Well Jan's example was of Coda that uses 128-bit internal file ids. > > > and if so, why don't we fix *THAT* instead > > Hmm, sometimes you can't fix the world, especially if the filesystem > is exported over NFS and has a problem with fitting its file IDs uniquely > into a 64-bit identifier. Note, it's pretty easy to fit _anything_ into a 64-bit identifier with the use of a good hash function. The chance of an accidental collision is infinitesimally small. For a set of 100 files: 0.00000000000003% 1,000,000 files: 0.000003% And usually (tar, diff, cp -a, etc.) work with a very limited set of st_ino's. An app that would store a million st_ino values and compare each new to all the existing ones would be having severe performance problems and yet _almost never_ come across a false positive. Miklos - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/