When server computers need to use the same data, a Network File System (also called NAS, or Network Attached Storage) can be used.
The Network File System is implemented using a File Server and a network. The File Server is a regular computer or specialized OS that has a regular File System and regular disk devices controlled with this File System.
The Network File System "stubs" running inside the OS kernel on "client" computers are "dummy" File Systems that retranslate application file requests to the File Server, using the network:
In this example, the File System on the File Server serves requests from several applications running on server "client" computers.
The only difference with the single OS is in the request delivery; instead of internal communication between an application and the File System running inside the OS kernel, the "stub" sends the requests via the network, receives the responses, and passes them to the application. All "real work" (File Allocation Table and cache maintenance) is done on the File Server computer.
Since only the File Server computer has direct access to the physical disk, all applications running on server systems use the same File System - the File System running on the File Server. That File System guarantees the data consistency. If the disk block 13477 is allocated to File2, it will not be allocated to any other file - until File2 is deleted or is decreased in size to less than 7 blocks.