6.5.1

Table Of Contents
Cause
vSphere DRS does not load balance FT VMs (unless they are using legacy FT). This limitation might
result in a cluster where hosts are unevenly distributed with FT VMs.
Solution
Manually rebalance the FT VMs across the cluster by using vSphere vMotion. Generally, the fewer FT
VMs that are on a host, the better they perform, due to reduced contention for FT network bandwidth and
CPU resources.
Losing Access to FT Metadata Datastore
Access to the Fault Tolerance metadata datastore is essential for the proper functioning of an FT VM.
Loss of this access can cause a variety of problems.
Problem
These problems include the following:
n
FT can terminate unexpectedly.
n
If both the Primary VM and Secondary VM cannot access the metadata datastore, the VMs might fail
unexpectedly. Typically, an unrelated failure that terminates FT must also occur when access to the
FT metadata datastore is lost by both VMs. vSphere HA then tries to restart the Primary VM on a host
with access to the metadata datastore.
n
The VM might stop being recognized as an FT VM by vCenter Server. This failed recognition can
allow unsupported operations such as taking snapshots to be performed on the VM and cause
problematic behavior.
Cause
Lack of access to the Fault Tolerance metadata datastore can lead to the undesirable outcomes in the
previous list.
Solution
When planning your FT deployment, place the metadata datastore on highly available storage. While FT
is running, if you see that the access to the metadata datastore is lost on either the Primary VM or the
Secondary VM, promptly address the storage problem before loss of access causes one of the previous
problems. If a VM stops being recognized as an FT VM by vCenter Server, do not perform unsupported
operations on the VM. Restore access to the metadata datastore. After access is restored for the FT VMs
and the refresh period has ended, the VMs are recognizable.
Turning On vSphere FT for Powered-On VM Fails
If you try to turn on vSphere Fault Tolerance for a powered-on VM, this operation can fail.
vSphere Troubleshooting
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