Simulation of demand paging in a local-area network with heterogeneous workstations
Mostapha Ziad · 1986
A system consisting of a number of workstations attached to a token-ring local-area network is considered. Every workstation attached to the network is capable of supporting a demand paging multiprogramming environment where memory is managed using the working set policy. A workstation is either diskless or has a disk and can act as a file server. We assume that there are D diskless workstations in the network. A simulation model is developed for this system, and is used to (1) investigate the behavior of demand paging over a network and its impact on the performance of such a network, (2) determine the number of diskless workstations that gives the best level of performance, (3) analyze the tradeoffs between the total number of workstations in the network, the number of diskless workstations, the number of dedicated file servers, and the characteristics of the jobs running in the workstations, (4) show that (a form of page caching in a workstation with a disk) is a viable technique to improve performance in such a system. The results obtained using this simulation model verified the feasibility of using demand paging over a network, and allowed us to determine the optimum number of diskless workstations (for a given total number of workstations in the network) that gives a desired level of performance. We also verified that localization improves performance and reduces the network traffic, especially in cases where the number of diskless workstations is more than 35% of total number of workstations and the jobs running in the workstations that have a disk are bound (i.e., most of their references are to remote file servers). The simulation model is easily modifiable and can thus be used to explore other issues of interest as well.