RAID 1+0 on Promise Fastrak S150 TX4

[Molle Bestefich]

Teemu Ikonen wrote:
> I'm trying to migrate a RAID 1+0 array on a Promise S150 TX4 card with
> 2.4.x kernel and the ft3xx.o module to a 2.6 kernel based system.
> 
> Unfortunately, it seems that dmraid supports only either RAID 1 or
> RAID 0, but not the combination (RAID 10) on this card.

Based on a quick glance of the code in
dmraid/lib/format/ataraid/hpt.h, I'd say that currently it probably
only supports PDC RAID 0, 1 and SPAN.


> The ft3xx module gives the following information on the array:

[ snip 4x Maxtor 6Y200 / 203928MB disks ]

> Dmraid tells the following:
> 
> # dmraid -tay
> pdc_cebbhcjedc: 0 792968704 mirror core 2 512 nosync 4 /dev/sdc 0 /dev/sdd 0
> /dev/sde 0 /dev/sdf 0

Just to clarify (if you're having a hard time with the dmsetup
nomenclature - I know I am!):
dmraid is trying to assemble a mirror from the 4 devices above with a
total size of 792968704 512-byte sectors.  That's a 4-way mirror that
has a capacity of 94.5 MB.  Knowing that disk manufacturers are
cheating bastards when it comes to size figures, that's almost exactly
half of one of your 200 "MB" Maxtor disks.

> ERROR: dos: reading /dev/mapper/pdc_cebbhcjedc[No such file or directory]
> 
> Contratry to above the device file /dev/mapper/pdc_cebbhcjedc exists,
> but mounting it fails.

That is probably a bug somewhere in dmraid/lib/format/partition/dos.c.

> Is there anything I could do to help get the RAID 10 support on TX4 to
> work with  dmraid?

I'm not the one to tell if there is, but I can definitely recommend
digging into the code.  It's extremely well-written, with great
commenting dispersed at exactly the right intervals.  I'd start with
dmraid/doc/dmraid_design.txt, which is about 5-6 pages.  Scroll down
to "Code directory tree" if you want to dig right in.  For starters,
you should probably get dmraid to recognize your array correctly by
fiddling with dmraid/lib/format/ataraid/pdc.*.