Design of a network filing system
Paul Michael McLellan · ERA · 1981
This thesis considers the issues involved in the design and implementation of a filing system for a large open inhomogeneous computer network.The filing system proposed is implemented on a number of file servers, that is, computers attached to the network specifically for this purpose.The view as seen by other client computers on the network is of a single coherent filing system, even though for efficiency and reliability the individual file servers are largely autonomous.The facilities and guarantees available do not vary with the location of files, so that sharing of remote files is easy. in particular, there is a single scheme for textnaming files which is almost completely free of restrictions.There is also a network wide security scheme for permitting and preventing access to files by other users and programs.The most important guarantee given by the filing system is that of consistency.Irrespective of concurrent access by other clients, and of crashes of either servers or clients, consistency of files is preserved.Old versions of all files, not just those which are completely rewritten, are retained for a time so that consistent views of the past are available.This permits a consistent backup snapshot to be taken of part of the filing system whilst it is active.Consistency is preserved by atomic transactions, and a commitment scheme is developed which is faster and more suited than most others to an ordinary filing system. FAThe five main problem areas then are: *data transfer primitives; *naming and location of files; *security of files against unauthorised access; *preservation of consistency in the face of crashes; *increasing .performanceby using local discs at clients.