Summary

We have seen the introduction of the NFS distributed file system. NFS is centered around the idea of simple and fast recovery in the face of server failure and achieves this end through careful protocol design. Idempotency of operations is essential; because a client can safely replay a failed operation, it is OK to do so whether or not the server has executed the request.

We also have seen how the introduction of caching into a multiple-client, single-server system can complicate things. In particular, the system must resolve the cache consistency problem in order to behave reasonably. However, NFS does so in a slight ad hoc ...