A cluster of 32 high-performance hosts was used to run three demanding Hadoop applications. The performance of native and several VMware vSphere® configurations was compared. The apples-to-apples case of a single virtual machine per host shows performance close to that of native. Improvements in elapsed time of up to 13% can be achieved by partitioning each host into two or four virtual machines, resulting in competitive or even better than native performance. The origins of the improvements are examined and recommendations for optimal hardware and software configuration are given. Apache Hadoop provides a platform for building distributed systems for massive data storage and analysis  using a large cluster of standard x86-based servers. It uses data replication across hosts and racks of hosts to protect against individual disk, host, and even rack failures.