From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:59308 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755028AbaFCXyb (ORCPT ); Tue, 3 Jun 2014 19:54:31 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1WryXG-00017Q-3K for linux-btrfs@vger.kernel.org; Wed, 04 Jun 2014 01:54:30 +0200 Received: from cpc21-stap10-2-0-cust974.12-2.cable.virginm.net ([86.0.163.207]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 04 Jun 2014 01:54:30 +0200 Received: from m_btrfs by cpc21-stap10-2-0-cust974.12-2.cable.virginm.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 04 Jun 2014 01:54:30 +0200 To: linux-btrfs@vger.kernel.org From: Martin Subject: Re: What to do about snapshot-aware defrag Date: Wed, 04 Jun 2014 00:54:14 +0100 Message-ID: References: <5388ED6B.8000706@fb.com> <538C7A79.8070407@fb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 In-Reply-To: <538C7A79.8070407@fb.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 02/06/14 14:22, Josef Bacik wrote: > On 05/30/2014 06:00 PM, Martin wrote: >> OK... I'll jump in... >> >> On 30/05/14 21:43, Josef Bacik wrote: >>> Hello, >>> >>> TL;DR: I want to only do snapshot-aware defrag on inodes in snapshots >>> that haven't changed since the snapshot was taken. Yay or nay (with a >>> reason why for nay) >> >> [...] >>> >>> === Summary and what I need === >>> >>> Option 1: Only relink inodes that haven't changed since the snapshot was >>> taken. [...] >> Obvious way to go for fast KISS. >> >> >> One question: >> >> Will option one mean that we always need to mount with noatime or >> read-only to allow snapshot defragging to do anything? >> > > Yeah atime would screw this up, I hadn't thought of that. With that > being the case I think the only option is to keep the old behavior, we > don't want to screw up stuff like this just because users used a backup > program on their snapshot and didn't use noatime. Thanks, Not so fast into non-KISS! The *ONLY* application that I know of that uses atime is Mutt and then *only* for mbox files!... NOTHING else uses atime as far as I know. We already have most distros enabling reltime by default as a just-in-case... Can we not have noatime as the default for btrfs? Also widely note that default in the man page and wiki and with why?... *And go KISS and move on faster* better? Myself, I still use Mutt sometimes, but no mbox, and all my filesystems have been noatime for many years now with good positive results. (Both home and work servers.) Regards, Martin