From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Sandeen Subject: Re: Do we need dump for ext4? Date: Thu, 28 Aug 2008 14:13:44 -0500 Message-ID: <48B6F8E8.8090308@redhat.com> References: <48B6BD02.3080307@redhat.com> <20080828184804.GN26987@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: ext4 development , Ric Wheeler To: Theodore Tso Return-path: Received: from mx2.redhat.com ([66.187.237.31]:36766 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753222AbYH1TPe (ORCPT ); Thu, 28 Aug 2008 15:15:34 -0400 In-Reply-To: <20080828184804.GN26987@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: Theodore Tso wrote: > On Thu, Aug 28, 2008 at 09:58:10AM -0500, Eric Sandeen wrote: >> I was talking to Ric about dump benchmarks, and he was of the impression >> that dump may not be used that often anymore, at least in the >> enterprise. > > Many people don't use the dump/restore any more program any more, > that's definitely true. Whether people use backups (as opposed to > large amounts of RAID) in the enterprise is a different question. I'm > not so sure about the second question. > > So a couple of comments. First, it's probably not fair to use > different backup programs for the different filesystems. Well, if a filesystem has a dedicated, presumably optimized backup utility, why would you not benchmark that as part of the mix? :) > We probably > want to do one set of comparisons where we use tar for all three. Yep, I'm doing that now ... also realized I tested on an inappropriate elevator (cfq) for a fancy-raid. I'll resend in a bit. > (Note: not all backup/dump programs are doing the right things with > xattr's, so we're not necessarily comparing programs with completely > identical functionality.) well, tar supposedly is with the options I gave it, xfsdump certainly does, and dump, I dunno offhand. > Secondly, it really wouldn't be hard to update dump/restore for ext4. > It uses libext2fs, so the real problem is that it is explicitly > checking the feature flags. Removing those checks may be all that is > necessary, given that ext2_block_iterate() still works for > extent-based files. Eh, I'll test that then. > I just noted BTW that the dump/restore doesn't > seem to be TOTALLY abandoned. It was last updated in 2006, true, but > there is support for backing up and restoring extended attributes and > ACL's. Ah, ok, so they all should be backing up acls/attrs then. > I wonder if they broke format compatibility with BSD 4.4 > format dump/restore backups when they did it --- and if anyone would > still cares. :-) > > Finally, I suspect most of the problem with using tar is the HTREE > dirent sorting problem. If we modify tar to sort the directory > entries before emitting the files, and then use that tar across all > the filesystems, I suspect the results would be much more better for > ext3 and ext4. True enough, just testing what we have now. I can play with acp... -Eric