From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Turmel Subject: Re: Issue with Raid 10 super block failing Date: Mon, 19 Nov 2012 08:39:57 -0500 Message-ID: <50AA36AD.4080100@turmel.org> References: <50A82267.9030802@turmel.org> <50A8F247.8060002@turmel.org> <50A91487.70806@turmel.org> <50A92F53.5080100@turmel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Drew Reusser Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi Drew, On 11/18/2012 02:10 PM, Drew Reusser wrote: [trim /] > Sorry - did not know the rules about top posting. Is there something > specific in the dmesg you are looking for? I tried to mount it again > and copied everything in the buffer. Here's what I wanted to see: > [270303.640240] EXT4-fs (md0): VFS: Can't find ext4 filesystem This suggests that the ext4 superblock isn't near the beginning like it's supposed to be. One of the ways that happens with MD raid is if someone does "mdadm --create" and destroys their old raid superblocks. I went back and looked at: > Creation Time : Thu Nov 15 16:08:02 2012 and: > Data Offset : 262144 sectors So you've re-created the MD array. That's bad. Chunk size and Data offset size and alignment defaults have changed in the past couple years, so re-creating an array with a different mdadm version can cause these problems. You can also lose the original order of devices, with similar consequences. (Side note: there's various pieces of advice floating around the internet on recovering a broken array that start with re-creating the array. It's horribly wrong, and only a last resort, and only after recording all the details about the original array.) Unless you kept a copy of "mdadm --examine /dev/sd[abde]1" for the original array, this will be difficult to debug further. Your best chance is to go back to the version of mdadm available when you first built the system and recreate with that, trying the various device order combinations. Don't attempt to mount to check for success. First, use "fsck -n" to non-destructively check the FS. If that gives few errors, then you can mount the FS. Phil