From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:48299 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750882Ab3HQEgb (ORCPT ); Sat, 17 Aug 2013 00:36:31 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1VAYFa-0002H9-5S for linux-btrfs@vger.kernel.org; Sat, 17 Aug 2013 06:36:30 +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 ; Sat, 17 Aug 2013 06:36:30 +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 ; Sat, 17 Aug 2013 06:36:30 +0200 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: 4 vol raid5 segfault on device delete Date: Sat, 17 Aug 2013 04:36:12 +0000 (UTC) Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Craig Johnson posted on Fri, 16 Aug 2013 11:50:59 -0500 as excerpted: > I have a 4 device volume with raid5 - trying to remove one of the > devices (plenty of free space) and I get an almost immediate segfault. > Scrub shows no errors, repair show space cache invalid but nothing > else (I remounted with clear cache to be safe). Lots of corrupt on bdev > (for 3 out of 4 drives), but I have no file access issues that I know > of. Thanks! Last I knew (kernel 3.10, where it was introduced, but I haven't seen any suggestion that 3.11 fixes all the problems yet), btrfs raid5/6 wasn't yet ready for anything like real use yet -- the all-OK code was there, but it couldn't yet cope with devices disappearing -- recreating the missing content from the checksums didn't yet work. So "an almost immediate segfault" might be expected if you actually remove a device from a btrfs raid5/6, because only the all-OK code is actually there, it's writing the checksums but it isn't prepared to actually use them yet. Btrfs raid0/1/10 should be usable, and /reasonably/ stable (for a filesystem still under development with bugs actively being fixed with each kernel release, that is), however (tho raid1 actually means two-way- mirror, no matter the number of devices). FWIW, I'm using btrfs raid1 here, but I have backups both to a second btrfs raid1 and to reiserfs (my previous filesystem and what I still use on "spinning rust, but it's not suitable for ssds, so I use btrfs on them), because btrfs IS still experimental. -- 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