Executive summary

From the perspective of an IT executive, read a short summary of the results and conclusions from the performance tests conducted in the study described in this paper. The provided information may help to make decisions about provisioning hardware and software resources for your enterprise.

The Large Memory Support and the HiperDispatch features introduced with z/VM® 6.3 significantly improved the resource overcommitment behavior, as opposed to z/VM 6.2. In addition, the use of EDEV-SCSI devices for z/VM paging allowed substantially higher memory overcommitment levels when compared to using ECKD™ paging devices. z/VM 6.3 with EDEV-SCSI paging devices can be highly recommended for environments running at high memory overcommitment levels.

It is also substantiated that different types of applications behave very differently when operated in resource constrained virtualized environments. Especially Java™ based middle-ware reacted comparatively sensitive when z/VM real memory was constrained. On the other hand, applications performing mainly disk I/O or network intensive operations turned out to be robust with respect to z/VM memory overcommitment. A database BI workload was even able to increase its throughput in some z/VM resource constrained scenarios, probably due to its use of highly sophisticated caching and workload scheduling capabilities. When operating a z/VM environment with limited real memory and processor resources, a well-balanced mix of applications is recommended in order to achieve a uniform utilization of available system resources.