Virtual File System
Sun Microsystems introduced one of the first Virtual file systems on UNIX based systems. A virtual file system or VFS refers to a programming that provides an interface amid an operating system's kernel and a more concrete file system.
The virtual file system acts as an abstraction layer that provides application access to various file systems, local and network storage devices. For a similar reason, a VFS may also be termed as a virtual file system switch. It also controls the data storage and retrieval between the operating system and the storage sub-system. The VFS sustains a cache of directory lookups to permit easy location of frequently accessed directories.