Re: [PATCH] sata_mv: Fix broken Marvell 7042 support.

[Mark Lord <liml@rtr.ca>]

Mark Lord wrote:
> Mark Lord wrote:
>> Hein-Pieter van Braam wrote:
>>> I zero'd all the disks, and now they show up as 'new' in the highpoint
>>> BIOS again... so, I guess there IS some reserved part somewhere that's
>>> accessible with the sata_mv driver.
>> ..
>>
>> Yeah, that's my suspicion too.. they must have just simply moved
>> the metadata to near the end instead of sector-8.
>>
>> Mmm...  I'll try a smaller drive here,
>> and zero the entire drive, then reboot with it
>> on the Highpoint board, and then see what sector it modified.
>>
>> This'll take a while.
> ..
> 
> Actually, it doesn't take long at all,
> with some creative use of fdisk.
> 
> And I haven't yet figured out their logic,
> but here's what I've found.
> 
> They write their RAID metadata near-ish to the end of the drive.
> On my 320GB drives, it ended up at about -199853 sectors from
> the end of the drive.  I have no idea what logic leads to them
> choosing such a peculiar location for it.
..

Correction:  Metadata begins at sector -191192 on my drive.

> 
> That's NOT an even cylinder or anything else I can figure out.
> 
> But if you leave the last 100KB of the drive unallocated for any 
> partitions, then your data might survive.
> 
> This needs more research, and probably another patch of some kind
> in the driver for #upstream-fixes.  I'm busy with a course all week,
> this won't happen (from me) until the weekend.
> 
> What a screwy BIOS.