Re: Moron Destroyed RAID6 Array Superblocks

Ok--I got moved in to my new place and am back and running on the 'net.
I sat down for a few hours and attempted to write a script to try all
possible combinations of drives...but I have to admit that I'm lost.

I have 8 drives in the array--and I can output every possible
combination of those.  But what the heck would be the logic to output
all combinations of the 8 drives using only 6 at a time?  My head hurts.

-A

On Sun, 2007-04-08 at 08:21 -0700, Andrew Burgess wrote:

quoted

After reading through the linux-raid archives I have been lead to
believe that I can recover my array by doing a --create and listing the
7 drives in the exact order I originally created them in.  Is this correct?

quoted

If so, the kernel upgrade managed to shuffle the drive names around...is
there any way I can figure out what order they should be in?

If you know the old order just boot the old kernel and recreate there

If you are using kernel rpms, you always want to 'install' new kernels
and not 'upgrade', that keeps both the old and new kernel available.

Otherwise, if you pick just 5 for the 7 drives from a raid 6 array
it seems to me you have 5 factorial combinations = 120. You could write
a script that tries them all and then tests by trying a read-only mount?

Good luck. I mashed a 3.5 TB array once by rerunning the lvm
creation which zeros the first chunk of the resulting device. I was
used to mdadm not hurting user data when creating. Grrr.

BTW when you test recreate the array make sure you dont start syncing, thats
another reason to just use 5 drives.

HTH

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