hard drives and dvr

I'm planning on buying this set up from ebay. http://www.ebay.com/itm/8CH-960H-HDMI-Video-DVR-NVR-Outdoor-900TVL-IR-Cut-CCTV-Security-Camera-System-/291520133755?

After I bid on this I saw that it didn't come with a hard drive? I'm just curious how long of record time would I have before it started looping? Will it even record without a hard drive. I'm really uneducated when it comes to this. However, we need a system cause within the last month a lawnmower and weed eater was stolen from the house. Then yesterday our neighbor said some guy was creeping around hiding in the bushes. So anyone who can help me would be great.

For 1 Ch analog camera for 960H sized recording, you can assume Max 2 Mega Bits per Second for the file size. Based on this number 2Mbps, you may calculate/ expect the size of HDD and its overwriting period (weeks or month) for looping.

For many businesses I work with, they opt for the DVR/NVR to record only when motion is detected. This gives a couple of benefits:

* Extends hard drive before looping...for the analog system you linked, it could be months before looping

* It's much (much) easier to go back and find a specific video clip of an incident

However, some business models do need a 24/7 constant recording, but for most of the situations for business or residential, the motion recording option fits the bill.