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

Fri Mar 2 21:25:17 UTC 2012
Digimer <linux at alteeve.com>

On 03/02/2012 04:20 PM, Bowie Bailey wrote:
> 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.

Ya. When I do use four drives, I simply create a four-member RAID level
1 array... Keeps it simple and, frankly, any performance gain from other
(mixed) levels would be easily missed.

E-Mail:              digimer at alteeve.com
Papers and Projects: https://alteeve.com