Have a NW 6.5 server with a 600gb NSS partition/volume. This is the
main data volume. This runs on a Dell 2800.

We need more space and have purchased an external storage unit (Dell
MD1000). Total usable storage for that new unit is 1.2tb.

Is it bad practice to split the volume onto 2 different RAID arrays?
Both original and new are RAID5.

Or should I just create a new volume and move some stuff pover there?

TIA - Jeff