This chapter introduces the following three commonly used High Availability (HA) tools: Clustering, VMware High Availability (HA) and VMware Fault Tolerance (FT). One of the key measures for enforcing HA is redundancy on the network and storage devices. The network is one of the weakest links in an IT infrastructure. Network redundancy ensures that the end users can remotely access the applications. VMware HA is a component of VMware that provides the automatic failover of virtual machines. VMware FT is another component of VMware that provides continuous availability. To protect the virtual machine, the VMware FT mechanism automatically creates an identical virtual machine; the original one is used as the primary machine, and the newly created one is used as the secondary machine. vMotion is a mechanism that enables the live migration of running virtual machines from one ESXi host server to another with zero downtime. Distributed Resource Scheduler (DRS) is a component of vCenter Server.