[linux-lvm] GRUB boot problem with lvm mirror type raid1

[g***@interia.pl]

Hi
I want to ask it is possible boot root file system (via GRUB) from LVM RAID1 volume?
I can boot root file system (with /boot) from linera LVM volume and from mirror volume, but when I create raid1 mirror GRUB can't boot from it:

lvconvert --type raid1 -m1 gsys/vsys

LVM mirror is work:
lvconvert -m1 gsys/vsys

I have two disk and use only LVM, not other raid software. GRUB have lvm module.
Thanks

[Peter Rajnoha]

Post by g***@interia.pl
Hi
I want to ask it is possible boot root file system (via GRUB) from LVM RAID1 volume?
lvconvert --type raid1 -m1 gsys/vsys
lvconvert -m1 gsys/vsys
I have two disk and use only LVM, not other raid software. GRUB have lvm module.

Grub doesn't support LVM RAID1 (it supports only RAID 4/5/6 type IIRC).

However, I don't recommend using /boot on LVM at the moment since
grub support for LVM is limited and unofficial. There's a plan to add
official and more robust support though - there are ongoing discussions
between grub and LVM team...

[g***@free.fr]

----- Mail d'origine -----
De: Peter Rajnoha <***@redhat.com>
À: ***@interia.pl
Cc: LVM general discussion and development <linux-***@redhat.com>
Envoyé: Mon, 14 Apr 2014 11:40:36 +0200 (CEST)
Objet: Re: [linux-lvm] GRUB boot problem with lvm mirror type raid1

Post by g***@interia.pl
Hi
I want to ask it is possible boot root file system (via GRUB) from LVM RAID1 volume?
lvconvert --type raid1 -m1 gsys/vsys
lvconvert -m1 gsys/vsys
I have two disk and use only LVM, not other raid software. GRUB have lvm module.

Grub doesn't support LVM RAID1 (it supports only RAID 4/5/6 type IIRC).

However, I don't recommend using /boot on LVM at the moment since
grub support for LVM is limited and unofficial. There's a plan to add
official and more robust support though - there are ongoing discussions
between grub and LVM team...

[Peter Rajnoha]

Post by g***@free.fr
--
Peter
Hello !
May I chime in on this ?
If the raid1 is made OUTSIDE lvm (ie soft raid1 giving /dev/md0 as a PV for LVM) will the Grub be apt to find it and boot ?
Or is it the same case as above ?
Thanks.

Grub should support MD RAID 0/1/4/5/6 and 10.

Though there's the same question about its limitations and
whether it's not similar to LVM support where we know that
an update in metadata format (e.g. adding new items or changing
the order of metadata items) can cause grub to not recognize
the volume anymore (since grub expects the metadata to be in
predefined and static form that doesn't change its layout in
future). There may be missing sanity checks too, like CRC checking
in case of LVM etc.

I'm not sure about LVM on MD at the moment. It depends on whether
grub supports device stacking. If grub supports iterative device/metadata
recognition, then yes, it's possible. (CC-ing phcoder to confirm)