There is no single way to store your data. A NAS - or Network Attached Storage box is the easy and increasingly popular answer because you can simply drag and drop files to/from any PC. I dare not for a second though suggest it is a "backup device" since I fear the mob of realists who will claim that no less than digging a 10 ft deep hole in your garden then dropping in a fire-safe full of tapes or disks is failsafe enough.
NAS boxes are a very low power way to store masses of data, while also giving everyone on the network access to that data. There are plenty of off the shelf generic-o boxes to choose from, but they are often hugely expensive or don't offer the precise features you want. Also, here at bit-tech we derive a certain satisfaction from doing stuff ourselves.