Re: RAID 1 and grub

[Richard Scobie <richard@sauce.co.nz>]

Keld Jørn Simonsen wrote:

>> # grub
>> grub> device (hd0) /dev/hdc
>> grub> root (hd0,0)
>> grub> setup (hd0)
> 
> I do not grasp this. How and where is it said that two disks are
> involved? hda and hdc should both be involved.

There are not two disks involved in this instance.

This is used in the scenario where the primary disk in the RAID1 
(/dev/hda), already has grub installed in the MBR and you wish to 
install it on the secondary drive (/dev/hdc).

This then allows for a failed primary drive to be removed and the 
machine to boot from the secondary - (may need BIOS to be set to boot 
from secondary drive).

As an aside, after last weeks discovery that the Fedora 8 install had 
not installed grub on the secondary drive, as part of a RAID 1 install, 
some cursory Googling and searching Redhat's Knowledge base leads me to 
believe that this may well be normal for all Redhat (RHEL/Fedora) RAID1 
installs.

One has nothing to lose by installing grub on the second drive in this 
case and it may save some delay in recovery on losing the primary, 
although as has been pointed out, it is best practice to test missing 
drives as part of initial install testing.

Regards,

Richard
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