From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adam Thompson Subject: Re: Big-endian RAID5 recovery problem Date: Mon, 01 May 2017 17:33:11 -0500 Message-ID: <8aa82733243a09e48ba87d6282d8f791@mail.athompso.net> References: <5c6e6e5d93d4056839e4f370e00a8e08@mail.athompso.net> <0ab1ea1b-8035-512e-0b0a-819e15929f41@youngman.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <0ab1ea1b-8035-512e-0b0a-819e15929f41@youngman.org.uk> Sender: linux-raid-owner@vger.kernel.org To: Anthony Youngman Cc: MUUG Roundtable , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 2017-05-01 16:59, Anthony Youngman wrote: > Get hold of lsdrv, and see what that tells you. (Look at the raid wiki > for details.) I don't know if it will have endian issues, but if it > doesn't an expert will probably be able to chime straight in and tell > you the create command. Ah! And that took me straight to the "asking for help" page. The raw data is here: https://gist.github.com/anonymous/321b6db3160c259c4a4dd549817a3d07 To summarize: * smartctl either fails to run or shows nothing wrong (depending on the vintage of drive, maybe?); * mdadm --examine fails to read the superblock because of the endianness issue (see https://raid.wiki.kernel.org/index.php/RAID_superblock_formats#The_version-0.90_Superblock_Format) * lsdrv fails to report any useful MD topology information I could see (other than confirming that each md device had four members, one partition on each drive) I also see 3 "FD" type partitions on each disk, but lsdrv only identifies *2* of them as belonging to an MD array. Not sure what's up with that. > The other thing is, read up on overlays because, if you overlay those > disks, you will be able to "create" without actually writing to the > disks. That way you can test - and even do a complete backup and > recovery - without ever actually writing to, and altering, the > original disks. Currently reading, thanks. Didn't know overlays could be used for block devices. Spinning up a QEMU instance of Linux-PPC or Linux-MIPS with the disks in pass-through mode has also been mentioned, but... ugh. Anecdotal reports from the web suggest that doing so would just be opening up a second rabbit hole in addition to the one I'm already headed down. -Adam