An archive preserves files that you no longer need on a short-term basis. An archive needs careful management. Backup on floppy disk Floppy disks are cheap, accessible, don't offer much storage and are rather unreliable if used as a working medium. They are best not used for archival purposes - their longevity is suspect. The file server is a collection of hard disks made available over the network.
Hard disks are generally reliable.
Backing up files on to the file server is sound practice. The file server is itself backed up on a weekly basis. They are similar in physical size and offer similar data transfer rates but they are much more reliable. At a low cost per disk they provide the best solution for archiving purposes. Like floppy disks they must be formatted before use but they are sold already formatted.