Re: on assembly and recovery of a hardware RAID

[NeilBrown <neilb@suse.com>]

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On Sat, Mar 18 2017, Alfred Matthews wrote:

> I've switched to the backup drives which are clones of the first, now,
> so destructive operations are ok if necessary. Also signatures will
> have changed.
>
> 0. Hm. Evidently the system is JHFS instead of HFS+, per the output
> below. Unsure if there is separate tooling in Debian.
>
> 1. Mount via
>
> mdadm --build /dev/md0 --level=0 -n2 --chunk=512K /dev/sdc2 /dev/sdb2
>
> works just fine. Thanks!
>
> 2. I'm still sticking with the non-destructive, non-mount edits for
> now. So I can report the following:
>
> hpfsck -v /dev/md0 | cat >> hpfsck_output.txt
>
> yields some stuff probably more enlightening than prior.

This is promising until:


> *** Checking Backup Volume Header:
> Unexpected Volume signature '  ' expected 'H+'

Here the backup volume header, which is 2 blocks (blocks are 8K) from
the end of the device, looks wrong.
This probably means the chunk size is wrong.
I would suggest trying different chunksizes, starting at 4K and
doubling, until this message goes away.
That still might not be the correct chunk size, so I would continue up
to several megabytes and find all the chunksizes that seem to work.
Then look at what else hpfsck says on those.

BTW, this:
> Invalid total blocks 2BA8CC68, expected 0 Done ***
is not a real problem, just some odd code.

NeilBrown

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