Vmware High Availibility

Vmware HA (VMHA)

In case of host failure all virtual machines running on dead ESXi host will be restarted on another ESXi host within the cluster.

HA Downtime is equal to Reboot time.

How does VMHA works ?

VMware HA continuously monitors not only ESXi host failure but also Guest OS failures in a cluster. Its install a agent on each host while placing it inside HA cluster a heartbeat with the other host in the cluster and loss of a heartbeat initiates the process of restarting all affected virtual machines on other hosts.

Uniform HA protection for all virtual machines and application no matters the OS or application support and admission control ensures that resources are available on host machines for CPU and RAM reservation while failure.

Requirement for VMHA

• Shared Storage for virtual machines running in HA cluster.
• Can use advance feature like DRS with VMHA or just VMHA only.
• vShpere Essential Plus, Standard, Enterprise, Enterprise Plus any of these licence
• At least two host in the cluster.
• Create a VMHA enabled cluster.

VMHA Master / Slave (FDMS)

• Master host per cluster known as the Fault Domain Manager Master (FDMS).
• FDMS host is determined via an election process.
• FDMS host with most mounted datastore has better election chances.
• VMHA checks per host failure using the management network and via datastore heartbeat.

Roles of FDMS host

• Monitors the state of slave hosts.
• Monitors the state of all protected virtual machines.
• Manages the list of cluster hosts and protected virtual machines.
• FDMS is vCenter management interface into the cluster health state.