Just a quick simple wizard of moving OpenVZ to another drive, since its stored in the plain folder of /vz
I presume you’ve already partitioned and formatted your drive (ext3 or ext4 works best), so we need to mount your new drive.
mkdir /vznew mount /dev/<DRIVE IDENTIFIER HERE> /vznew (find identifier via fdisk -l)
Now we need to turn off your OpenVZ VPSs and move the data, including -p to reserve permissions.
service vz stop cp -Rvp /vz/* /vznew/
Now we need to disable the old /vz folder and mount the new one as /vz
mv /vz /vzold umount /vznew mkdir /vz mount /dev/<DRIVE IDENTIFIER HERE> /vz service vz start
There you go, that should start all your OpenVZ VPSs from the new drive, you’re also need to tell the OS that you want it to mount that drive as /vz every time you boot.
You’re need to edit /etc/fstab and add this line,  remember to change the drive on the first part, and if your using a different drive format, change that too (ext3 etc)
/dev/sdc1 /vz ext3 defaults 1 1
So you should end up something similar to
LABEL=/ / ext3 defaults 1 1 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 LABEL=SWAP-sda2 swap swap defaults 0 0 /dev/sdc1 /vz ext3 defaults 1 1