Fasttrack TX2000 RAID problem

Greg Felix greg.felix at
Fri Aug 26 16:15:41 UTC 2005

> Are the data on your disks expendable?
> I'd like to see what happens if you 'dd if=/dev/zero' metadata on both
> disks, swap their places (so the larger disk 2 becomes disk 1) and
> create a new RAID0 on them........

I just destroyed the RAID array, verified the metadata was wiped,
swapped the drives, and created a new RAID0.  The metadata for each
disk was placed in the same sector as before.  The only difference is
now dmraid can find the metadata on hdg instead of hde (The disks
being swapped of course).

One interesting thing I found is that in the FastTrack setup screen it
shows: (I'm using 'Disk 1' as pre-swapped Disk 1):

Disk 1 = 40016MB
Disk 2 = 39999MB

If I convert those numbers to sectors like so:

40016*1000*1000/512 = 78156250 sectors
39999*1000*1000/512 ~= 78123047 sectors

These numbers are of course rough, and I don't know why they're using
1000 instead of 1024, but the numbers are really close to where the
metadata is being found as I'll copy again below:

> Disk 1:
> found at 78156225
> out of 78156287
> = 63 from end
> Disk 2:
> found at 78123969
> out of 78165359
> = 41391 from end

Just out of curiosity I used the inverse of that function on the "out
of #" lines above and got

Disk 1 ~= 40016MB
Disk 2 ~= 40020MB

So this is proof to me that the BIOS is reading Disk 2 as 21MB (or
41000 or so sectors) less than the kernel is.

So where's the problem? The BIOS? The Kernel? The IDE disk? And why
does the RAID work in Windows?

Appreciate your help

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