Modelling parallel access to shared resources in a distributed file system using queueing networks
This paper presents a practical and noniterative method for evaluating queueing networks in which delays due to locking of files are represented using measurable parameters. A queueing network model of a distributed file system is introduced. The model allows read and write locks and allows multiple classes of users to be represented. The model parameters are estimated from the values of measurable quantities. An approximation of branching probabilities is used to direct transactions to their original sites when they leave a remote host. The service times of lock servers are calculated as functions of the loads on all service centers. The various lock granularities may be represented by this model. Performance measures applicable to the evaluation of computer systems are introduced and evaluated. An example involving a distributed file system and measurement data collected in a small business installation is given to compare performance measures and locking delays provided by the simulation and analytic models for various lock granularities.