On 26/04/2012 03:37, Bill Davidsen wrote:

John Robinson wrote:

[...]

quoted

Without either hardware or BIOS RAID, you can still end up being
unable to boot,
e.g. the BIOS will try to boot from the first hard drive present, but
if it has
bad sectors in the MBR or /boot partition, booting may fail even
though there's
a perfectly good mirror on the second drive, because the BIOS doesn't
understand
RAID. This has happened to me :-(

Doesn't need to understand RAID, just be willing to try the next item in
the boot list on failure. My experience has been that almost every BIOS
will try the 2nd item if the 1st fails totally (ie. drive isn't there).
A _good_ BIOS will try the next item on sector error in the MBR.

Absolutely - but in the case I had, grub couldn't load its next stage 
because of a sector error.

It probably didn't help that the weekly array scrubs don't touch the 
space between the MBR and the first partition, where that code lives.

After that the BIOS needs to understand a lot more to do anything
smart after the MBR runs.

Agreed; only a RAID BIOS (software e.g. IMSM or hardware RAID card) 
could have saved me from the above failure.

Cheers,

John.