From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vn0-f48.google.com ([209.85.216.48]:42419 "EHLO mail-vn0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751638AbbGOPpS (ORCPT ); Wed, 15 Jul 2015 11:45:18 -0400 Received: by vnbf62 with SMTP id f62so4959864vnb.9 for ; Wed, 15 Jul 2015 08:45:17 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <55A63F03.2080207@gmail.com> References: <55A4F74D.9000305@gmail.com> <55A50DBF.1080602@gmail.com> <55A63F03.2080207@gmail.com> Date: Wed, 15 Jul 2015 09:45:17 -0600 Message-ID: Subject: Re: BTRFS raid6 unmountable after a couple of days of usage. From: Chris Murphy To: Austin S Hemmelgarn Cc: Chris Murphy , Btrfs BTRFS Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Wed, Jul 15, 2015 at 5:07 AM, Austin S Hemmelgarn wrote: > I've managed to get the other filesystems I was having issues with mounted > again with the device= options and clear_cache after running btrfs dev scan > a couple of times. It seems to me (at least from what I'm seeing) that > there is some metadata that isn't synchronized properly between the disks. OK see if this logic follows without mistakes: The fs metadata is raid6, and therefore is broken up across all drives. Since you successfully captured an image of the file system with btrfs-image, clearly user space tool is finding a minimum of n-2 drives. If it didn't complain of missing drives, it found n drives. And yet the kernel is not finding n drives. And even with degraded it still won't mount, therefore it's not finding n-2 drives. By "drives" I mean either the physical device, or more likely whatever minimal metadata is necessary for "assembling" all devices into a volume. I don't know what that nugget of information is that's on each physical device, separate from the superblocks (which I think is distributed at logical addresses and therefore not on every physical drive), and if we have any tools to extract just that and debug it. -- Chris Murphy