A network-attached storage (NAS) device is a data storage device that connects to and is accessed through a network, instead of connecting directly to a computer. … The beauty of a NAS device is that it can be easily accessed by multiple people, multiple computers, mobile devices, or even remotely. It’s quick and convenient, and it’s also a heck of a lot safer than lugging an external hard drive or USB memory stick around. … Many of the best NAS drives are able to hold more than one hard drive and can mirror that hard drive in case of failure. So, if one hard drive does go, your files are still intact on another.