The PI System has been expanded to support High Availability (HA) via a limited form of server and interface redundancy. Additionally, the PI System is easily virtualized via VMWare’s ESX cluster product. Corning has installed a Manufacturing Execution System (MES) to collect process and product data in a Life Sciences manufacturing application, and uses the PI System as both a process historian and a SCADA interface to heterogeneous process equipment. Availability of the MES and PI System are vital to allow timely collection of required product data and to support manufacturing operations where downtime has an immediate, negative, and quantified financial impact. The availability options and limitations of both a VMWare ESX cluster and PI HA will be described. Corning chose to use both PI HA and VMWare ESX clustering technologies to ensure operational uptime and increase system availability. Technical considerations and the trade-offs in using PI HA and VMWare ESX will be reviewed and the final system architecture and several technical “watch outs” will be discussed. Real-life failover scenarios will illustrate the complementary nature of PI HA and VMWare clusters, plus examples of how this system has performed to date. Future needs around both PI HA and VMWare will be discussed.