Almost ever commercial level product has a hard drive or hard drives and records over the video.... when properly programmed. There are a number of things that you want to be able to set,,, one is motion recording. This will only record and use drive space ( or potentially bandwidth) when the camera sees motion. The frame rate... which can be set as high as 30 frames per second. Should be down around 7 unless your looking at alot of fast moving activity. Etc etc. There are alot of tweaks that can be done in order to save both drive space and bandwidth. On top of that you set this system to recycle say anywhere from 2 weeks to 2 months depending on the amount of drive space you use. With motion detection on that varies with how much activity your camera sees and whether you have set them up correctly.
A number of companies make decent systems with good or better remote access and expandable drive space. The cheapest ive used is HIK Vision. There stuff is good.. not my favorite and their support is ok. For you that want to build out your own pc id use Geovision. Software is free with them. Their support is just ok.... i no longer will build out a pc for this. PCs run into issues over time. Id stick with a more hardware based solution such as the HIK or one of the better brands. I love 3xlogic. Not expensive, made in usa, excellent tech support, great online access options, hardened recorder... lots of options. You cant go wrong with 3x. They also have the Infinias line of access control that integrates with your video so card access also gives you a recording tied to it making looking up stuff super easy. And god forbid your not their and the cops show up and need a video to go... you can do that remotely for them and all someone has to do is stick in a blank dvd for you.
We spend ridiculous amounts on a still and barely blink.... step up a little and get a good surveillance system. Perhaps you will never need it. But the day you do you will feel it was the best money you ever spent.