Although in this both devices are used as the devices for storage something, there is a big difference between NAS Unit and San Unit. NAS stands for Network Attached Storage, while SAN is Storage Area Network both of them is your solution as storage for your network. It depends on the type of data that you store in this storage devices, the use of the storage, and the network building to choose one of this storage devices. You can see the different in both of them is that there are two different things the way to connect the storage, the use of input and output protocol and the type of cable used in this storage.
NAS Unit vs. SAN
NAS is the Unit device works as one network server that storage many files from the network to the server, which is, also can shares its storage to the other user of the network. It uses Ethernet connection over the repeater, router or the other system that can connect to more than one network systems. The NAS is simplest can be accessed if both NAS or computers connect together user IP address or MAC address for the more specific connection. If you differentiate between NAS and SAN in the way they do they computing program, NAS Unit is more to be a server for the network that has its features and also has the own storage that can share using its own program.
If you use NAS, you can get a complete NAS network system than SAN. If SAN is used as interface program, in server and clients network or the bigger is Local Area Network, NAS is used to connect to wider area networks so to fulfill the needs of hundreds or thousands of clients with the server, and you can use NAS bought from https://www.nasunit.com over the other network storage such as San or DAS.