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    Configuring Fault Tolerance

    VMware vSphere fault tolerance provides continuous availability for virtual machines by creating and maintaining a secondary VM that is identical to, and continuously available to replace, the primary VM in the event of a failure. The feature is enabled on a per virtual machine basis. This virtual machine resides on a different host in the cluster, and runs in virtual lockstep with the primary virtual machine. When a failure is detected, the second virtual machine takes the place of the first one with the least possible interruption of service. Because the secondary VM is in virtual lockstep with the primary VM, it can take over execution at any point without interruption, thereby providing fault tolerant protection.

    Figure 1: VMware Fault Tolerance

    VMware Fault Tolerance

    The primary and secondary VMs continuously exchange heartbeats. This exchange allows the virtual machine pair to monitor the status of one another to ensure that fault tolerance is continually maintained. A transparent failover occurs if the host running the primary VM fails, in which case the secondary VM is immediately activated to replace the primary VM. A new secondary VM is started and fault tolerance redundancy is reestablished within a few seconds. If the host running the secondary VM fails, it is also immediately replaced. In either case, users experience no interruption in service and no loss of data. VMware vSphere HA must be enabled before you can power on fault tolerant virtual machines or add a host to a cluster that already supports fault tolerant virtual machines. Only virtual machines with a single vCPU are compatible with fault tolerance.

    For configuration instructions for VMware fault tolerance, see:

    Preparing Your Cluster and Hosts for Fault Tolerance

    The MetaFabric 1.0 solution test bed features VMware fault tolerance (Figure 2). This was tested as part of the solution on the port group “PG-Fault tolerance-107”. VMkernel is bound to this port group. Once fault tolerance is enabled on a VM, a secondary VM is automatically created.

    Fault tolerance is also enabled on Windows domain controller VM (running on one compute node in the POD1 cluster).

    Figure 2: VMware Fault Tolerance on POD1

    VMware Fault Tolerance on POD1

    Published: 2015-04-20