Performance Enhancement of SMP Clusters with Multiple Network Interfaces Using Virtualization

Clusters of small-scale SMP/CMP nodes are becoming increasingly popular due to their cost-effectiveness. As these nodes are typically capable of supporting a number of network interfaces similar to the number of CPUs, the issue arises how to optimally configure the cluster for optimum communication performance. This paper evaluates a number of configurations on a 4-CPU Opteron cluster with multiple Gigabit Ethernet interfaces. Techniques include channel bonding and using independent communication pathways. With the latter, the use of virtualization via the Xen Virtual Machine Monitor offers the best potential to parallelize all stages of message transmission, for the case when multiple CPUs on a node are communicating simultaneously. Network-level microbenchmarks indicate the best performance is achieved with a configuration where guest virtual machines running on each CPU communicate directly with a dedicated interface, bypassing the virtual machine monitor. Channel bonding also proved to be more effective over multiple communication streams than over single.