> It could be caused by (fx.):
> - Promise deciding to move the metadata around on disk
> - An "odd" configuration that causes the PDC BIOS to place it
> somewhere that dmraid did not expect
> - dmraid may think that some value in the PDC metadata is constant
> and regard it as part of PDC magic, when it's actually a variable
> value..
>
> (And a number of other, less likely reasons.)
>
> I'm unfamiliar with PDC metadata - does RAID devices have names in the PDC BIOS?
> If they do, you could find the metadata on disk by searching for this name.
> It's usually plain ASCII encoded, and usually resides somewhere at the
> beginning or end of the disk. Try finding it with 'hexedit' or
> 'strings'. You may find the dmraid source code, particularly
> /lib/format/ataraid/pdc.{c,h} useful.
>
> The source code is, btw, extremely well-written. So it might also
> help you to dive in (esp. the above mentioned file) and add some debug
> statements to the metadata detection code.
>
> Another thing you can do (it's a long shot, but hey) is to post your
> BIOS version number. If there's any regressions against the PDC BIOS,
> we'll know circa when it has happened. Also, others might have
> success with RAID 0 and your firmware version..
I've had some success in debugging this today and here's what I've
found. It appears that the metadata for the first disk (that dmraid
if correctly finding) is 63 sectors from the end of the disk. I would
assume that the metadata for the second disk would be in the same
place, but it's not. I found it instead 41000 or so sectors before
that. When I modify dmraid and recompile so it's looking for this
exact sector it find the metadata and seems to setup the array
correctly. The question is of course WHY is the metadata there
instead of at the end? Here's what I think. I think the BIOS is
coming up with a different number of sectors on the disk than Linux
is. When it lays down the metadata it's putting it at totalNumber-63
whereas the kernel is getting a different value. The two actual hard
drives aren't the same type so this might play into it.
I tried upgrading the firmware of my Fasttrack TX2000 from 2.00.0.24
to 2.00.0.33, but it seems to be setting up the metadata is the same
strange place. Any thoughts on any of this would be appreciated.
Here is some info of where I found the metadata for each disk
Disk 1:
found at 78156225
out of
78156287
= 63 from end
Disk 2:
found at 78123969
out of
78165359
= 41391 from end
What do you think?
Greg
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