Re: RAID Questions
On Fri, Jul 9, 2010 at 4:10 PM, Miles Fidelman
<mfidelman@meetinghouse.net> wrote:
> Tom H wrote:
>>
>> On Tue, Jul 6, 2010 at 8:15 PM, Miles Fidelman
>> <mfidelman@meetinghouse.net> wrote:
>>
>>
>>>
>>> shell> grub-install hd0
>>> shell> grub-install hd1
>>>
>>
>> With these grub-install invocations, you will not be able to boot in
>> degraded mode.
>>
>> You have to set both sda and sdb to hd0 but you cannot do that in
>> device.map. You have to use the grub shell:
>
> I'm pretty sure you're wrong on this - at least it's worked for me in the
> past.
>
> You DON'T have to set both sda and sdb to hd0 - what you have to achieve is:
>
> 1. have identical bits in /boot on both drives - so that they can be read
> before the raid array gets created
> -- if you've built with RAID-1, and done a standard install, this happens
> automatically
>
> 2. get grub installed on the MBR of both drives - so your BIOS can boot off
> either drive
> -- grub-install does this for you
>
> 3. set up your BIOS to fallback to sdb if sda fails to respond
>
> 4. set up your menu.1st to boot off sdb if sda fails to respond
>
> I'm pretty sure that things will break badly if grub things that both disks
> are hd0.
It is a standard procedure to ensure that you can boot from a degraded
raid1 array:
http://en.gentoo-wiki.com/wiki/Software_RAID_Install#Installing_Grub_onto_both_MBRs
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