Re: My Thecus RAID-0 filesystem unmountable with mdadm. Please help.
am 24.05.2010 23:57:50 von Michael Evans
Way too big and spread out, I don't know if anyone will have the time
to read that.
First, https://raid.wiki.kernel.org/index.php/RAID_Recovery
Second, what parameters do you remember about the original array?
Third, you probably want to try hexdumping the first megabyte or two
of each drive and looking for a superblock of your filesystem.
(man hexdump)
hexdump -Cn $((1024*1024)) /dev/whatever
You may also want to use dd to get the end of the block device.
Most importantly, knowing //where// the superblock is in your device
will allow for a guess about where in to the block-dev the data is
supposed to start. That ///may/// allow for the creation of a
superblock with the proper alignment (and hopefully chunk size) to
read your data.
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Re: My Thecus RAID-0 filesystem unmountable with mdadm. Pleasehelp.
am 25.05.2010 07:57:12 von Mikael Abrahamsson
On Tue, 25 May 2010, Neil Brown wrote:
> As far as I can tell from all the details you provided, everything is
> behaving as expected except that the filesystem looks bad. It could be that
> the Thecus NAS vendors made some incompatible change in the ext3 filesystem
> format for their product. I would rate that as fairly unlikely but
> definitely possible. I believe it has happened before.
Yes, I tried putting some NAS drives (don't remember the brand) into a
regular linux box and I could read most but not all files, and my research
back then indicated that they had some kind of mix of ext3 and ext4 on
there that was not in the mainline kernel.
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Mikael Abrahamsson email: swmike@swm.pp.se
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Re: My Thecus RAID-0 filesystem unmountable with mdadm. Please help.
am 28.05.2010 03:32:11 von Michael Evans
I was suggesting the hexdump utility to determine several things:
1) Which disk contained the extfs magic header (thus the first disk in
almost all cases)
2) Where the start of that header was, which would /typically/ begin
after 1kb of padding (it's there for other things to use in some
cases).
3) If created properly, the extfs header /may/ give you a suggested
stripe/chunk size.
As an example...
http://www.virtualblueness.net/Ext2fs-overview/Ext2fs-overvi ew-0.1-12.html
http://www.monstrmoose.com/repository/Halo_Tools/Etc/WinHex_ 15.1/Ext%20Superblock.tpl
(0x400 == 1024)
Looking at the blocks, in the standard output the 'magic signature'
should be in the 4th row, starting halfway across, which it is for
even ext4 filesystems. Typically, but not always, there is
zero-filled padding around this area; as denoted by the line of 0s and
then the * indicating that the last line repeats until the next
address.
hexdump -Cn2048 /dev/mapper/lin-lucid--root_crypt
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000400 90 97 05 00 ff 56 16 00 f3 1d 01 00 a3 4b 04 00 |.....V.......K..|
00000410 2f 95 02 00 00 00 00 00 02 00 00 00 02 00 00 00 |/...............|
00000420 00 80 00 00 00 80 00 00 d0 1f 00 00 ec 1e e6 4b |...............K|
00000430 32 d3 e0 4b 11 00 1f 00 53 ef
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