Introduction

In this chapter we will learn how to enable and configure vSphere HA to react to host failures.

vSphere HA (High Availability) is a feature that can reduce unplanned virtual machine downtime. It does this at both the host and the virtual machine level. At the host level, it will monitor for host failures or network isolations and react accordingly. Depending on how it is configured to react, it can choose to restart or not restart the VMs that were running on a failed host. At the virtual machine level it can detect guest operating system and application failures and restart the virtual machines.

Starting with vSphere 5, HA has been completely recoded. It is also referred to as the Fault Domain Manager. It no longer uses Legato's AAM. The earlier concept of primary and secondary master has been relinquished as well.

With FDM, only one ESXi host among all the hosts in the cluster can become the master. The remaining hosts are slaves. During the master election process, a host with...