6.7

Providing Fault Tolerance for
Virtual Machines 3
You can use vSphere Fault Tolerance for your virtual machines to ensure continuity with higher levels of
availability and data protection.
Fault Tolerance is built on the ESXi host platform, and it provides availability by having identical virtual
machines run on separate hosts.
To obtain the optimal results from Fault Tolerance you must be familiar with how it works, how to enable it
for your cluster, virtual machines and the best practices for its usage.
This chapter includes the following topics:
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How Fault Tolerance Works
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Fault Tolerance Use Cases
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Fault Tolerance Requirements, Limits, and Licensing
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Fault Tolerance Interoperability
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Preparing Your Cluster and Hosts for Fault Tolerance
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Using Fault Tolerance
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Best Practices for Fault Tolerance
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Legacy Fault Tolerance
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Troubleshooting Fault Tolerant Virtual Machines
How Fault Tolerance Works
You can use vSphere Fault Tolerance (FT) for most mission critical virtual machines. FT provides
continuous availability for such a virtual machine by creating and maintaining another VM that is identical
and continuously available to replace it in the event of a failover situation.
The protected virtual machine is called the Primary VM. The duplicate virtual machine, the Secondary
VM, is created and runs on another host. The primary VM is continuously replicated to the secondary VM
so that the secondary VM can take over at any point, thereby providing Fault Tolerant protection.
VMware, Inc.
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