What's in a Filesystem?
As we stated earlier in this article, a filesystem is a data structure designed to implement the abstraction of files and directories. As such, there are dozens of types of filesystems possible. Berkeley UNIX currently offers three flavors of filesystems: UFS, NFS, and MFS.
- UFS, like many other filesystems, manages to impress its underlying files and directories on a bulk storage media such as magnetic moving head disks. In particular, UFS uses placement algorithms to schedule head movement and rotational delay to improve average filesystem effectiveness.
- NFS, the Network Filesystem originally designed by Sun Microsystems, funnels program requests for files over a network connection, which is then satisfied by a server machine's own filesystems. Consequently, these files can be located quite a distance away from the actual computer whose program is referencing a file.
- MFS, a memory-based filesystem, stores temporary files in the processor's virtual memory storage areas for rapid access to transient data. It evolved from RAM-based disks used on many MS-DOS systems and uses virtual memory to provide a way to keep active files present in RAM while gradually moving inactive portions back to the disk.
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