[Nottingham] Big biiig problem regarding IDE-RAID

Robert Davies nottingham at mailman.lug.org.uk
Tue Jul 15 14:09:01 2003

On Tuesday 15 Jul 2003 13:50, Rob Andrews wrote:
> [15-Jul-2003 13:26.53 (BST) / Graeme Fowler]
> You may be aware that the majority of the low-end IDE RAID chipsets
> (HighPoint, Promise, etc) are not real RAID chipsets at all. They have
> their own RAID format for checksumming and suchlike, but the implementation
> is purely done in software - both from a Linux and Windows driver
> perspective. The only difference being that the BIOS implements a fair
> amount of the software RAID in order to install and boot from the array.

It's possible to boot off a RAID-1 /boot & / partitions, did it earlier this 
year using lilo, and the RAID-BOOT HOWTO.  The BIOS actually just needs to 
read off one partition, that makes part of the mirror md device, then on disk 
failure if you're lucky the 2nd half of the mirror is automatically promoted 
to the boot disk by the BIOS, or you may need to change the boot drive letter 
and all should be well.

The method I used involved using initrd's, and provided LVM support 
additionally (though I'd not recommend using that for /).  I think Grub's 
boot line editting feature, might be useful for awkward cases, though I've 
not tried it out, I think it does support RAID-1.

> But as far as I'd be concerned... I'd have used Linux's own software RAID
> instead of a vendor's binary-only software RAID module.

Yes,  yes!!!  Beware of Vendors brings 'solutions' laced with heavy amounts of 
Marketing B/S  :)