From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:58790 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750727AbaDMECt (ORCPT ); Sun, 13 Apr 2014 00:02:49 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1WZBd2-0007kK-65 for linux-btrfs@vger.kernel.org; Sun, 13 Apr 2014 06:02:48 +0200 Received: from ip68-231-22-224.ph.ph.cox.net ([68.231.22.224]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sun, 13 Apr 2014 06:02:48 +0200 Received: from 1i5t5.duncan by ip68-231-22-224.ph.ph.cox.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sun, 13 Apr 2014 06:02:48 +0200 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: very slow btrfs filesystem: any data needed before I wipe it? Date: Sun, 13 Apr 2014 04:02:36 +0000 (UTC) Message-ID: References: <20140407160506.GG10789@merlins.org> <5342CE0C.3070707@fb.com> <20140407185121.GI10222@merlins.org> <5342FD3D.3090905@fb.com> <20140407200002.GL1809@merlins.org> <20140409173842.GT10789@merlins.org> <20140325014956.GG11533@merlins.org> <20140412202542.GW7322@merlins.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Marc MERLIN posted on Sat, 12 Apr 2014 13:25:42 -0700 as excerpted: > If I mount with ro,recovery, then it's actually normal speed to copy > data off it, quite weird. It seems like btrfs' background processes are > grinding the FS down to a halt, and I didn't turn on autodefrag. What happens if you simply mount it ro, without the recovery option? Is it still normal-speed or is that slow as a rw mount? Speed hasn't been an issue here, but FWIW I normally keep my rootfs ro mounted as I decided that's lower risk in the event of a system crash or power outage and I don't actually /need/ it rw most of the time (I have a dedicated /var/log, /home on an entirely separate btrfs, and the bits of /var that need to be writable in normal operation symlinked into /home/var/), only mounting the rootfs rw to update or do other system maintenance. If a ro filesystem is normal speed but rw slow, the problem must be in the write path, which is what I suspect. If a ro filesystem is slow and only a recover,ro filesystem is fast, then there's something strange going on with btrfs internals that recovery obviously bypasses. Knowing one way or the other should definitely help to pin things down. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman