CephFS is a POSIX-compliant file system ontop of a Ceph cluster. CephFS can be used on any number of clients simultaneously and changes are immediately applied to all clients. With CephFS you get a scalable file system that you can use as usual to store your data.
In Linux servers you can make this completely transparent for the respective application. Whenever you need more space, you just need to expand your cluster to instantly store more data in the same file system.