dmraid comments and a warning

[Reuben Farrelly]

On 7/02/2006 9:08 a.m., Dax Kelson wrote:
> This isn't purely a Linux problem. Any operating system using fake RAID1
> needs to be robust in this regard. I saw a Windows box using 'fake'
> motherboard RAID and the motherboard BIOS got flashed which reset the
> "Use RAID" setting to 'off'. Then Windows booted off of half the RAID.
> This was noticed and the BIOS setting was turned back on and a boot
> attempted. Massive corruption and a dead Windows system was the result.
> To Window's credit I haven't seen it accidentally boot off of half the
> RAID as long as the BIOS RAID was turned on and the drivers installed.

Very interesting to read this post - as you're not the only one to have this 
problem.  I had this exact same problem after a BIOS upgrade a few months back 
whereby all settings got reset and I booted up off one half of the raid - to 
find massive trashing after I went back in and fixed the BIOS setting and 
reactivated the second half of the raid and then rebooted.  (read: ntdetect.com 
and friends did not exist anymore)

It's the sort of stuff that should flag big red flashing boxes and warning 
messages appearing, but you like I, had to learn the hard way ;-)

My box has a genuine Intel D945 board, so it's hardly a cheap-and-nasty piece of 
hardware even if it has a cheap and nasty type of RAID.  At the time I put it 
down to a "don't do that, it's probably a BIOS bug which I'll never hit again" 
type issue.
I suspect but haven't tested that the best way around the problem after this 
sort of unplanned configuration change is to completely wipe the second 
old/removed drive so it no longer looks like a RAID disk at all, fix the bios 
setting, boot up on the one original device and re-add the second drive as a new 
device in the array, while booted up under Windows.

On my Linux server which is another box, I have disabled onboard RAID1 and use 
mdadm instead, which seems smarter (and safer) ;-)

reuben