I have LVM RAID 1 (not mdadm RAID 1, but exactly LVM2 RAID 1) for my root partition. I would like to make my system boot without either of the HDDs where the underlying PVs of the root LVM partition reside.

The kernel launch line in grub.cfg (automatically generated by GRUB2) looks like:

linux   /kernel-genkernel-x86-3.11.7-hardened-r1-3 root=/dev/mapper/vg-root ro dolvm

It looks perfectly with both disks enabled and the system is HDD fault-tolerant runtime, i.e. it works properly if either of HDDs are down during runtime.

However, if I try to boot without one of HDDs, I am getting

Refusing activation of partial LV root. Use --partial to override.

during boot and kernel panic. From one side it seems reasonable since it's not a normal behavior for lvm to launch when one of PV is absent. However, it's absolutely necessary in order to boot server. The potential workaround I can think of is adding some additional option to kernel launch line.

Do you know how to make the LVM RAID 1 work for root partition when on of HDDs does not work?