Re: Question about LVM or RAID on /boot

[Chris Murphy]

On Oct 14, 2013, at 10:22 PM, Kun Huang <address@hidden> wrote:

Hi all

When searching why we couldn't use LVM or RAID on /boot, the most of answers are "that couldn't be support". But I would like get to know more details. In grub.conf file, we could use (hd0,0) to specify "root=". In another words, grub in stage2 actually could find data in all of disks. Is this right? If grub could find all partitions of all disks, what other reasons stop we find out information of LVM or RAID about and in disks?

Works fine with GRUB2 for the past ~2 years at least. Probably longer.

The limitation is BIOS seeing all of the disks, not a GRUB limitation. I think there's work that needs to be done to update the GRUB LVM code when it comes to LVM integrated raid levels 10, 5, and 6; and also thin provisioning. Except for raid0, 1, 10, I think the rest is a bit esoteric for /boot, and is probably more trouble than it's worth if there are device failures. 

I don't actually know off hand if GRUB2's md raid code can rebuild data chunks from parity on the fly, e.g. if there's a 1 disk failure of a raid5 array. If not, yeah, all the more reason I'd keep /boot simple.

Chris Murphy