DVRstunted

I'm looking to install a 16 Camera System at my business, and I need some help figuring out which way to go. I currently have a Speco DVR-16TN that I was going to use as the basis for my system, but It wont have the storage capabilities (on board) that I will need. (I will need to hold all Recorded Data for 6-8 months). Are there any external storage options for standalone DVR's like this one (Aside from burning everything to DVD/CD?) Or should I consider going with a PC Based System instead?