Analytical model of inter-node communication under multi-versioned coherence mechanisms

Our goal is to predict the performance of multi-node systems consisting of identical processing nodes based on single node profiles. The performance of multi-node systems significantly depends on the amount of inter-node communication. Therefore, we built an analytical model of the communication amount, i.e., the number of transfers of cached copies, on multi-node systems with coherence mechanisms that support multi-versioning. Multi-versioned mechanisms are assumed because databases are most likely to be the bottleneck and because a typical clustered database has one of these mechanisms. In our model, the number of transfers of copies of a block per write access is expressed as a function of a write ratio, the number of nodes, and the lock down factor which denotes how many versions of copies can exist. To empirically verify our analytical and theoretical model, we compared the number of transfers that predicted by our model and that counted by a toy simulator of multi-versioned mechanisms.