MC78 Homework 5 (Fall 1998)

Due: December 4, 1998

NFS (the Network File System) has various parameters the system administrator can set. One is how large a chunk of data should be read or written in a single request (i.e., a singe RPC). The maximum size is 8Kbytes. Which would typically give better performance: a small value or a large value for the request size? Why?
Another NFS parameter the system administrator can set is the timeout time, that is the length of time the client should wait for a response from the server before retrying the request. First, suppose the connection to the server is very reliable, but the server is sometimes heavily loaded. Would you prefer a short timeout or a long one under these circumstances? Why? Now suppose instead that the connection is rather unreliable, but the server is generally lightly loaded. Would you now prefer a short timeout or a long one? Why?
Actually, the timeout length set by the system administrator only is used for the first attempt to make each request. If the request needs to be retransmitted, the timeout is doubled the second time, and doubled again the third time. Explain why NFS is designed this way.
Do exercise 18.7 from page 593.