Re: md extension to support booting from raid whole disks.

[Goswin von Brederlow <goswin-v-b@web.de>]

Gabor Gombas <gombasg@sztaki.hu> writes:

> On Wed, Apr 29, 2009 at 12:43:51PM +1200, Daniel Reurich wrote:
>
>> In which case your probably using a hardware raid controller anyway so
>> not our problem.  Otherwise if the array is broken by a failed
>> controller we probably shouldn't boot of it anyway.
>
> I have set up a box with 8 SATA disks attached to 2 on-board
> controllers. The BIOS can boot from any of the controllers, but then it
> can only see the disks that are attached to the selected controller.
> Which is quite reasonable if the BIOS handles the controller selection
> by redirecting INT 13h (I have not checked).
>
> With "/" on RAID1, I can boot in any failure scenarios (I've actually
> tested that anno). With your setup, the box would never boot, since it
> could never access enough disks in a RAID5/6 array, even if all the
> disks/controllers are perfectly fine.

So you have lost nothing. It doesn't boot now from raid5 (accross all
disks) and it still doesn't boot from raid5 with the proposal. Your
hardware just doesn't support it.

>> What's specifically dangerous about it?  Define the failure modes that
>> this scheme is unable to either cope with that it should do.
>
> There is no need for a failure mode. Your scheme does not work even when
> everything is fine.
>
> Gabor

It would only be a problem if with the proposal things would get
worse.

MfG
        Goswin