A distributed file system is a file system that enables multiple computers across a network to share access to files. This shared access allows for both files and storage mediums to be shared across the network. This can enable computers with minimal storage to access and modify large files.
Many modern file systems allow for the use of "file sharing" with other network computers. This is an example of a distributed file system. In these cases, the only files that are accessible to users on the network are those that have been intentionally shared by the user.
A file system can be considered a distributed file system only if it fits two qualifications. The first is that the system must enable multiple users to access files from different computers through a network. The second requires that the file system not be located on a physical disk that is shared by each of the computers. If the file system is located on a disk that is shared by the computers, then it is known as a shared disk file system.
There are many advantages to using a distributed file system over a shared disk file system. Shared disk systems enable each user to access the memory disk directly. This allows each computer to have a high degree of control over the memory disk, which can potentially be a security risk. Distributed file systems instead allow indirect access through a network protocol.
The use of indirect access through network protocols allows for the central storage device to regulate access to files for all users. This can range from allowing some users read-only access to files to even denying any access to particular files. By centralizing this control, a distributed file system minimizes potential security holes.
Another related system is known as a distributed data store. This system is similar and allows for users to store information across a variety of network systems. In return for this, users accessing the distributed data store will allow other users to store information on their system.
The difference between a distributed file system and a distributed data store is often blurred. The primary difference generally comes from the different settings for the use of these systems. Distributed file systems generally are used on local area networks, restricting access from users outside the network. By contrast, distributed data stores often have users from many different networks.