Disk /dev/sdc doesn't contain a valid partition table
That's not an error. Its simply saying that there is no partition table on sdc.
You don't necessarily need a partition table. A lot of people actually setup
their system like this, especially when the device is from a SAN.
--- Physical volume ---
PV Name /dev/sdc
LVM is using the correct device. You don't need to change anything.
[root server ~]# pvscan
PV /dev/sdc VG raid_vg0 lvm2 [744.97 GB / 480.00 MB free]
Total: 1 [744.97 GB] / in use: 1 [744.97 GB] / in no VG: 0 [0 ]
--Dave