I have 14 cameras (all 3MP with the exception of 4 4MP) hooked up to our NVR. The NVR has two WD hard drives installed, (1) 3TB and (1) 4TB. Prior to installing the second drive I was getting about 3 days worth of data saved before it overwrites. But since I've added the second hard drive Im still getting just 3 days, and it states neither drive has free space. So is it recording the same info to both drives? Or how do I get about 6-7 days on these two drives?