The problem is at boot time you may get a failed reference to /dev/cdrom
It is caused by the LVM mounting tools trying to probe a cdrom device.
You need to edit the LVM conf to "filter" out cdrom devices and not try to probe them.
How to reproduce the problem:
/dev/cdrom: open failed: No medium found
How to fix the problem:
# vi /etc/lvm/lvm.conf
You can only have [one] filter active at a time, the default probes everything.
Comment that filter line out, then add this filter line in:
filter = [ "r|/dev/cdrom|" ]