Hey all, since my grandpa's farm has been broken into one too many times, I'm going to help him invest in a security system for his farm. Here's the situation, camera's have to be outdoor, sturdy (Iowa weather), and resolution has to be, at a minimum, basic high definition. Looking for a 6-8 camera system, with a hard drive. I'm pretty good with electronics, but this isn't an area I'm well versed in. Prefer wireless, since, you know, farm. Many that I've been looking at offer around a 500 GB hard drive/DVR, how much does this realistically store? Also, are these hard drives made to store information until its full, and then simply override it once it becomes full? Basically just looking for recommendations, and a little knowledge of the products. Would it also be possible to hookup a larger external hard drive to store more video longer? Obviously, we want to be able to see whos been doing this, so I don't want it to become erased from the HD before we can view. Thanks!