The 5U NAS is a network attached Storage server. Basically, one can load as many drives as possible (20 in this case), and combined the storage space into one massive drive. There are safety measures to take in place to assure that data loss is minimal. In this instance, the 20 drives will only have 18 used for storage calculation. Therefore, if each drive is an 12TB drive, then the server will show itself as a 216TB drive. The 5U server can be essential for either a media server, or a NAS server.
A Media Server is a server that holds media files. This will include pictures, music, or videos. One could store all of their content in “separate” drives so E:/ might be for pictures, F:/ might be music, and so on. Default saves could be to these virtual drives which will be on the media server. As with all computers, there must be a minimum of 128GB NVME for the OS, and 2 should be acquired for RAID-1 capability. The media content will store either on mechanical hard drives that typically have larger capacities, or SSDs that are faster, and more reliable.
A NAS (Network Attached Storage) server is intended to provide a resource for hosting less used but essential files, as well as act like a backup. Many experts recommend having a backup system that is 4 times the capacity of the drive. This means a 128GB storage should have 512GB of backup storage. It is not recommended to plug in external drives to the server. This is because if the external hard drive fails, then you lose that content. If a single drive fails in a NAS server, then the system has backup of your backup in place. It will mark that drive as dead, and send a message to the owner that the particular drive is dead. This will give time for the owner to buy a new drive, and allow the server to rebuild the drive’s content.