[CentOS] CentOS 6.2 software raid 10 with LVM - Need help with degraded drive and only one MBR

Fri Mar 2 21:20:44 UTC 2012
Bowie Bailey <Bowie_Bailey at BUC.com>

On 3/2/2012 4:00 PM, Jonathan Vomacka wrote:
> On 3/2/2012 2:46 PM, Bowie Bailey wrote:
>> On 3/2/2012 1:01 PM, m.roth at 5-cent.us wrote:
>>> Digimer wrote:
>>> <snip>
>>>> Boot from a live CD using the CentOS 6.2 install media. Once booted:
>>>> <bash># grub
>>>> <grub>  root (hd0,0)
>>>> <grub>  setup (hd0)
>>>> <grub>  root (hd1,0)
>>>> <grub>  setup (hd1)
>>>> <grub>  root (hd2,0)
>>>> <grub>  setup (hd2)
>>>> <grub>  quit
>>>> <bash># reboot
>>>> This assumes that grub sees the drives at '0, 1 and 2' and the boot
>>>> partition is the first on each drive. If it is, when you type 'root
>>>> (hdX,0)' it should report that a file system was found. The 'setup
>>>> (hdX)' will tell grub to write the MBR to the specified disk.
>>> THANK YOU! I could have used that once or twice, and had no idea that grub
>>> could create a std. MBR.
>> When I set up a RAID 1, I do it like this:
>> device (hd0) /dev/sda
>> root (hd0,0)
>> setup (hd0)
>> device (hd0) /dev/sdb
>> root (hd0,0)
>> setup (hd0)
>> device (hd0) /dev/sdc
>> root (hd0,0)
>> setup (hd0)
>> This way, all the drives are set up as if they are hd0.  This way, any
>> of them will boot normally as a stand-alone drive.
> Bowie, in terms of RAID 10, each drive technically cant be standalone 
> right? The drives are striped and mirrored.

Right.  I was referring to RAID 1.  For a RAID 10, you would have to
find the proper drive to boot from.  This is why I tend to limit myself
to RAID 1 in software.  If I need something more complex than that, I
get a hardware card so the OS just sees it as a single drive and you
don't have to worry about grub.