Always keep the BPAV folder as is. Your footage may move to other NLE's that need the original BPAV. Our method of back up has progressed to more redundancy after loosing 2 HD. Start with Imagine products Shot Put Pro. Copy SxS to three destinations. We use (1) CAL Digit 3 TB Mirrored, (2&3) USB HD SEAGATE or G Tech. Send one USB copy with client, Mail second USB after confirmation of ingest. Erase CAL Digit and start over. A more secure process could involve LTO. Not many folks are ready to lay out $$. Since Sony now allows writing back to their optical disks User Data folders, we have added this along with the above. It requires a laptop and a Sony U1 Drive. I now sleep well.