I already had xfs_repair scan the entire 6TB (took it 56 hours, which is the
reason for the subject line). So it couldn't find a SB anywhere on that volume
and it walked all over it. Therefore I guess the SB has been overwritten by
something, maybe parted. As for the LVM physicals being in the wrong order, I
can try to reverse them but I'm really pretty sure I have it right. Still,
since the scan by xfs_repair couldn't find a SB anywhere I don't know what I
We don't have a backup of these volumes, but I'm told by the user that
almost all the data can be retrieved again from our archive, it's just a pain
in the neck to do that. So while it would be nice to recover it won't be
Before wrapping this up, if you could just clarify a couple things. If I
look at the bytes at the beginning of each physical part of the LVM's, what am
I looking for? "XFSB"? If I do find that byte string, why couldn't xfs_repair
find it when it did the scan and what do I do with it if I do find one? We see
a software product call ufsexplorer that claims to be able to recover data
without an XFS super block, anybody try it?
I appreciate your help and time,
---- Original message ----
>Date: Sat, 17 Mar 2007 06:37:22 +1100
>From: David Chinner <dgc@xxxxxxx>
>Subject: Re: Should xfs_repair take this long?
>To: Thomas Walker <walker@xxxxxxxxx>
>Cc: David Chinner <dgc@xxxxxxx>, xfs@xxxxxxxxxxx
>On Fri, Mar 16, 2007 at 11:15:12AM -0400, Thomas Walker wrote:
>> So maybe I got bit the same way. parted may be overwritten something
>> at the head of the volume.
>Doesn't look like partition blocks at the start of each volume, though.
>> Is there any way to repair the super block
>> though? It seems that everyone agrees xfs can't do anything until it
>> has a super block somewhere and I don't seem to have one.
>That's beacuse repair can't work out where things are supposed to
>be without a superblock to tell it critical information.
>Manually trying to find and repair a superblock is a hit and miss
>affair - at this point we don't even know if the primary superblocks
>have been overwritten or whether something else is wrong with LVM...
>> If there's no
>> way to repair, then what about recovery?
>In a word: backups.
>> I see mention of possibly
>> doing an xfs dump to another disk, reformat the original volume, and
>> then xfs restore back. Is there any online procedure for how to do that
>> if it applies to me here?
>You need to be able to mount the filesystem to dump it, so until you
>can run repair there's no simple recovery option.
>If the lvm config is correct and repair cannot find a valid
>secondary superblock, then you really need to start doing dangerous
>things to try to recover. i'd suggest taking a copy of the lvm
>volumes before doing anything else.
>Then, find a secondary superblock in the volume (first 4 bytes of
>the sector are "XFSB" in hex) and copy that sector to block zero of
>the filesystem. If repair still won't do it's stuff, then you need
>to use xfs_db to modify that superblock until it does. Then when
>repair runs, you get to look in lost+found and try to work out what
>all the broken bits are.....
>SGI Australian Software Group