There isn't any limitation on the size of a swap file (or at least there hasn't been since 1999). The general rule of thumb that people use is to have twice your memory in swap. So if you have 1 GB of RAM, you want 2 GB of swap. That rule dates from back when memory was much more expensive. Many feel that creating more than 2 GB of swap is just a waste of harddrive space. Just remember swap isn't a replacement for memory. Even with solid state drives, if you are relaying constantly on swap things are going to slow down.