This paper begins with a brief overview of the problems of high availability (HA) and disaster recovery (DR) in the virtual environment. Due to server clustering, outages have the potential to affect many servers at once, possibly causing a corresponding failure among many mission-critical applications. The paper then presents several fundamental criteria for evaluating HA/DR solutions and reviews the components, architecture, and functional characteristics of two that are designed to protect critical applications on VMware ESX: VMware HA and Symantec Veritas™ Cluster Server for VMware ESX.