External hard disks are very suitable for data backups, for example. The disadvantage of such solutions is that the data can only be used by one connected device at a time. If you have several systems, you have to constantly reconnect them. A better data backup solution is achieved with a so-called NAS, which is basically a device that is not connected to a PC, but is accessible to all PCs or systems in the home network. Such solutions are also easy to set up, but you have to learn the ropes. The initial costs are a little higher, because in addition to the network storage system, there are also hard disks. In the long run, however, you are more flexible than with external hard disks and you also have additional possibilities, e.g. you can also use it to operate a multimedia server to play music, for example.