[Gllug] Hardware RAID On-Disc Format

[Mike Brodbelt]

On Mon, 2004-03-15 at 14:08, Bruce Richardson wrote:
> On Mon, Mar 15, 2004 at 01:54:42PM +0000, Doug wrote:
> > OK Good point, I omitted to say that this is two disks in a simple
> > mirror :)  For striping certainly you wouldn't expect to be able to
> > recover anything useful from either software or hardware raid.
> 
> Ah, now, that may be different.  Only way to be sure is for you to shut
> down the machine and then try accessing one of those disks as an
> individual device.

If it works I'd be surprised. Certainly, none of the HW RAID controllers
I've used have an on disk format which is OS readable. With a mirror,
you might be lucky, and there might be an OS recognisable filesystem,
but I'd expect it to be encapsulated within a controller specific
"envelope", so you'd probably need to scan the physical disk to find the
starting sector, and manually tweak the partition table to make the
partition mountable.

Another big thing to bear in mind is endianness. Intel/AMD machines are
little endian, but many RAID cards use a big endian microprocessor as
the RAID controller. So, even if you can find the partition, you may
need a different CPU architecture to mount it. Of course this is also FS
dependant, as some filesystems (XFS) have the same on disk format
regardless of the endianness of the host CPU.

Mike.

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