Is this more about how many streams and simultaneous connections can be open at one time? I have a DR4300 and it will only accommodate four VTLs. I thought I was supposed to make a VTL for every backup I did, each server having it's own VTL on a big NAS somewhere (when you don't have an appliance.) On top of that, page 6 in the Best Practices for VTL manual looks like VTL is better than a regular NetVault Backup VTL.
My point is that if I want to organize the way I want, I have to use the NVBU VTL. I also don't want to lose any compression the DR gives.