[dm-devel] Re: [PATCHSET] block,scsi,libata: implement alt_size

[Tejun Heo]

Dan Williams wrote:
> On Thu, Apr 30, 2009 at 1:00 PM, Jeff Garzik <jeff at garzik.org> wrote:
>> Tejun Heo wrote:
>>> Hello,
>>>
>>> Jeff Garzik wrote:
>>>> <shrug>  I suppose...
>>>>
>>>> It just seems like a nasty hack, but unfortunately I don't see
>>>> anyone stepping up to do it properly -- with a DM device
>>>> automatically layered on top that splits the device into separate
>>>> regions: one block device for the 'regular' area, and one for the
>>>> HPA.
>>> Isn't that more hacky?  I don't know.  All that dm needs to know is
>>> the location of the metadata which is located w.r.t. the end of the
>>> device which might be at a different location if BIOS tried to pull
>>> silly stunts.  So, exporting the size BIOS might have used seems like
>>> a straight forward solution to me.
>> "<shrug> I suppose" is basically a reluctant ack, in the absence of other
>> solutions :)
>>
> 
> Couldn't the "fix" also just be a note to users to disable ignore_hpa
> if they notice that there raid arrays are not assembling correctly?

I don't know.  If it doesn't work automatically, the solution really
isn't worth much.  People generally don't (shouldn't need to) have any
idea what HPA is.  It basically boils down to "Linux doesn't support
RAID".  :-)

Maybe we should just put this issue to the rest and strongly advise
people against BIOS raids.

Thanks.

-- 
tejun