There are many different types of network storage options.

Hard Drive Array
A hard drive array is a storage device that holds inside of it several different hard drives running in conjunction with one another. This works to the user's benefit in terms of speed and back-up capabilities.

Removable Disk Library
Libraries are similar to arrays in that there are multiple pieces of the storage device. Removable disk storage, however, refers to a storage type such as a CD or DVD that can be filled and replaced, and that is stored outside of the device.

Network Storage Server
Most network storage devices do not act as a server for connected computers. This type, however, is not only a storage device but a server as well.

Network Hard Drive
This is a single hard drive that all connected computers can save information to.