Two drives with LUKS+LVM, only the first one can mount

Question

I have the following setup:

sda (new installation)
  sda1
  sda2
  sda3 (LVM-LUKS)
    root
    swap

sdb (old installation)
  sdb1
  sdb2
  sdb5 (LVM-LUKS)
    root (old)
    swap

The goal is to have sda3->root as / and sdb5->root as /home/user/other mounted at boot time.

Currently sda operates correctly during the boot, but sdb refuses to mount root or see its swap.

I have currently added a second line to /etc/crypttab, now it looks like this:

sda3_crypt UUID=uuid-for-sda3 none luks,discard
sdb5_crypt UUID=uuid-for-sda3 none luks,discard

This has resulted in the appearance of /dev/mapper/sdb5_crypt, and it links correctly to a newly-appeared /dev/dm-3. However, unlike sda3 it doesn't "expand" its partition table.

I have tried to boot into a live-usb, there i can mount either of the drives successfully; but i cannot mount both at the same time. This leads me to believe that it maybe a problem with some internal naming scheme, for example both maybe trying to usurp "xubuntu--vg-root" as the mapper name, and thus only the first one succeeds in that task.

Answer 1

The problem was the conflict in the name of LVM, both were titled xubuntu--vg. To resolve this issue one needs to first rename the virtual group with vgrename.