Naming Schemes of Distributed file systems

Large networks often use a systematic naming scheme, such as using a location (e.g. a department) plus a purpose to generate a name for a computer. However, smaller networks will frequently use a more personalized naming scheme to keep track of the many hosts. Network naming can be hierarchical in nature, such as the Internet's Domain Name System. Indeed, the Internet employs several universally applicable naming methods: Uniform Resource Names (URN), Uniform Resource Locators (URL), and Uniform Resource Identifiers (URI).
A good naming scheme is scalable, unique, and easy to remember. The purpose of these naming schemes is to name network computers, but it can also be used to name projects, variables, streets, pets, kids, or any other project where unique names and remember able names are required.

There are three main approaches to naming files:
 
- Files are named with a combination of host and local name.
* This guarantees a unique name.
* It is neither location transparent nor location independent.
* Same naming works on local and remote files.
- Remote directories are mounted to local directories.
* A local system seems to have a coherent directory structure.  
* The remote directories must be explicitly mounted. The files are location independent.
* SUN (Network File System)NFS is a good example of this technique.
- A single global name structure spans all the files in the system.
* The DFS is built in the same way as a local file system.
* It is location independent.

Naming and Transparency in Distributed File Systems

Naming is the mapping between logical and physical objects. In a conventional file system, it's understood where the file actually resides; the system and disk are known. In a transparent DFS, the location of a file, somewhere in the network, is hidden. File replication means multiple copies of a file; mapping returns a SET of locations for the replicas.

- Location transparency -
* The name of a file does not reveal any hint of the file's physical storage location.
* File name still denotes a specific, although hidden, set of physical disk blocks.
* This is a convenient way to share data.
* It can expose correspondence between component units and machines.

- Location independence :
* The name of a file doesn't need to be changed when the file's physical storage location changes.Dynamic, one-to-many mapping.
* Better file abstraction.
* Promotes sharing the storage space itself.
* Separates the naming hierarchy from the storage devices hierarchy.

A location independent naming scheme is a dynamic mapping, since it can map the same file name to different locations at two different times. Therefore, location independence is a stronger property than location transparency.
Most DFSs today support location transparent systems. They do not support migration and files are permanently associated with specific disk blocks.