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After reinstallation of my OS, I decide to manually assemble a RAID6 array.

# mdadm --assemble --auto=yes --scan=auto /dev/md0

I don't exactly remember a message but programmdadm return a resizing raid array.

$ more /proc/mdstat

Personalities : [raid6] [raid5] [raid4] md0 : active raid6 sdc1[0] sdf1[7](S) sdh1[6] sdd1[5] sdg1[4] sda1[3] sdi1[2] sdb1[1] 4883799680 blocks level 6, 64k chunk, algorithm 2 [7/7] [UUUUUUU]

After I try to run an encryption and:

# cryptsetup luksOpen /dev/md0 md0_crypt

Device /dev/md0 is not a valid LUKS device

I searched but I can't find in Internet how to solve this problem.

This is really bad, because they are a life's fotos/videos... :(

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You updated your backups before playing with mdadm, did you? –  S19N Jan 7 '12 at 16:01
What does "hexdump -C /dev/md0" show you? Show the first 16 lines. –  ott-- Jan 7 '12 at 22:43

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