On Fri, 2006-06-09 at 23:19 +0800, Feizhou wrote:
I just looked at the boot sector on the 3 machines that I have running software raid1. It looks like the installer got it right on all 3. IIRC, one was installed as CentOS 4.1, another as 4.2, and another as 4.3.
The installer will install grub. Just not properly. If the first disk dies, when the box comes up, the previous second disk grub stage 1 will load but it will not look for the stage 2 on the current disk and therefore fail.
That will depend on what your bios does when the first drive fails and whether you've had to move it to make it boot at all. On the scsi systems where I've used it, the 2nd drive will boot and everything on the cable shifts up if the first drive fails or is removed. IDE systems are different - and normally won't boot if a failed drive is still connected.
Hmm, does it come back up on a scsi based system?
Mine does but it may depend on the bios.
I cannot remember but if the second disk's grub stage 1 does get loaded, it tries to load stage 2 from the 'second' drive which will not work and the reason for the failure or whether it does load stage2 but stage2 looks in the wrong 'disk' for its config file.
So either way, it should also fail on a scsi system...
These seem to shift the first working drive into the first bios drive as well as /dev/sda. The same disk will boot whether I put it in the 1st or 2nd (SCA hot-swap) slot. I have noticed that some newer machines must be configured specifically for the slot to use when booting and are even unhappy if you swap in a different drive type in the same slot without reconfiguring the bios boot selection so this may vary a lot among machines.
I did the grub setup by hand but have noticed that there are different sets of instructions around that apply to IDE drives. In any case, I think it is a good idea to keep a rescue CD handy and understand how to re-install grub.