From: NeilBrown <neilb@suse.com>
To: Adam Thompson <athompso@athompso.net>,
MUUG Roundtable <roundtable@muug.ca>,
linux-raid@vger.kernel.org
Subject: Re: Big-endian RAID5 recovery problem
Date: Sat, 06 May 2017 15:57:17 +1000 [thread overview]
Message-ID: <87fugio7cy.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <5c6e6e5d93d4056839e4f370e00a8e08@mail.athompso.net>
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On Mon, May 01 2017, Adam Thompson wrote:
> So I've got 4 IDE HDDs, each with 3 RAID partitions on them, that were
> part of a RAID array in a now-very-dead NAS.
>
> Of course, I need to get data off them that wasn't backed up anywhere
> else.
>
> I've got a 4-port USB3 PCIe card, and 4 IDE/SATA USB adapters, and all
> the hardware seems to work. So far, so good.
>
> The problem is that the disks use the v0.90 metadata format, and they
> came from a big-endian system, not a little-endian system. MD
> superblocks *since* v0.90 are endian-agnostic, but back in v0.90, the
> superblock was byte-order specific.
>
> mdadm(8) on an Intel processor refuses to acknowledge the existence of
> the superblock. Testdisk detects it and correctly identifies it as a
> Big-endian v0.90 superblock.
>
> I'm reluctant to blindly do a forced --create on the four disks, because
> I'm not 100% certain of the RAID topology; there are at least two RAID
> devices, one of which was hidden from the user, so I have no a-priori
> knowledge of its RAID level or layout.
>
> The filesystems on the md(4) devices are, AFAIK, all XFS, and so should
> (hopefully) not have any endianness issues.
>
> I can't find any modern big-endian Linux systems... looks like all the
> ARM distros run in little-endian mode.
>
> Any suggestions on the best way to move forward?
>
Look for "--update=byteorder" in the mdadm man page.
NeilBrown
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next prev parent reply other threads:[~2017-05-06 5:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-01 21:39 Big-endian RAID5 recovery problem Adam Thompson
2017-05-01 21:59 ` Anthony Youngman
2017-05-01 22:33 ` Adam Thompson
2017-05-02 2:47 ` Phil Turmel
2017-05-02 7:29 ` [RndTbl] " Trevor Cordes
2017-05-02 8:59 ` Roman Mamedov
2017-05-05 19:22 ` [RndTbl] " Adam Thompson
2017-05-06 5:57 ` NeilBrown [this message]
2017-05-06 6:41 ` Trevor Cordes
2017-05-07 23:40 ` [mdadm PATCH] Mention "endian" in documentation for --update=byte-order NeilBrown
2017-05-08 17:42 ` Jes Sorensen
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