6.0

Store ISOs on Shared Storage for Continuous Access
Store ISOs that are accessed by virtual machines with Fault Tolerance enabled on shared storage that is
accessible to both instances of the fault tolerant virtual machine. If you use this configuration, the CD-ROM
in the virtual machine continues operating normally, even when a failover occurs.
For virtual machines with Fault Tolerance enabled, you might use ISO images that are accessible only to the
Primary VM. In such a case, the Primary VM can access the ISO, but if a failover occurs, the CD-ROM
reports errors as if there is no media. This situation might be acceptable if the CD-ROM is being used for a
temporary, noncritical operation such as a patch.
Avoid Network Partitions
A network partition occurs when a vSphere HA cluster has a management network failure that isolates
some of the hosts from vCenter Server and from one another. See the vSphere Availability publication. When
a partition occurs, Fault Tolerance protection might be degraded.
In a partitioned vSphere HA cluster using Fault Tolerance, the Primary VM (or its Secondary VM) could end
up in a partition managed by a master host that is not responsible for the virtual machine. When a failover is
needed, a Secondary VM is restarted only if the Primary VM was in a partition managed by the master host
responsible for it.
To ensure that your management network is less likely to have a failure that leads to a network partition,
follow the recommendations in the vSphere Availability publication.
Viewing Fault Tolerance Errors in the vSphere Client
When errors related to your implementation of Fault Tolerance are generated by vCenter Server, the Fault
Details screen appears.
This screen lists faults related to Fault Tolerance and for each fault it provides the type of fault (red is an
error, yellow is a warning), the name of the virtual machine or host involved, and a brief description.
You can also invoke this screen for a specific failed Fault Tolerance task. To do this, select the task in either
the Recent Tasks pane or the Tasks & Events tab for the entity that experienced the fault and click the View
details link that appears in the Details column.
Chapter 27 Providing Fault Tolerance for Virtual Machines
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