OK. so, I've been doing some tests, I've seen 10 min files at 100MB, and 300MB... so, if I take a HUGE ball park, and make 10 minutes at 500MB, that would be upwards of 70GB per day, per camera..
20 cameras, would be 1.4TB per day.
So, if I were to store the last 2 hours, on the "new" drive...