6.7
Table Of Contents
- vSphere Availability
- Contents
- About vSphere Availability
- Business Continuity and Minimizing Downtime
- Creating and Using vSphere HA Clusters
- Providing Fault Tolerance for Virtual Machines
- How Fault Tolerance Works
- Fault Tolerance Use Cases
- Fault Tolerance Requirements, Limits, and Licensing
- Fault Tolerance Interoperability
- Preparing Your Cluster and Hosts for Fault Tolerance
- Using Fault Tolerance
- Best Practices for Fault Tolerance
- Legacy Fault Tolerance
- Troubleshooting Fault Tolerant Virtual Machines
- Hardware Virtualization Not Enabled
- Compatible Hosts Not Available for Secondary VM
- Secondary VM on Overcommitted Host Degrades Performance of Primary VM
- Increased Network Latency Observed in FT Virtual Machines
- Some Hosts Are Overloaded with FT Virtual Machines
- Losing Access to FT Metadata Datastore
- Turning On vSphere FT for Powered-On VM Fails
- FT Virtual Machines not Placed or Evacuated by vSphere DRS
- Fault Tolerant Virtual Machine Failovers
- vCenter High Availability
- Plan the vCenter HA Deployment
- Configure the Network
- Configure vCenter HA With the Basic Option
- Configure vCenter HA With the Advanced Option
- Manage the vCenter HA Configuration
- Set Up SNMP Traps
- Set Up Your Environment to Use Custom Certificates
- Manage vCenter HA SSH Keys
- Initiate a vCenter HA Failover
- Edit the vCenter HA Cluster Configuration
- Perform Backup and Restore Operations
- Remove a vCenter HA Configuration
- Reboot All vCenter HA Nodes
- Change the Appliance Environment
- Collecting Support Bundles for a vCenter HA Node
- Troubleshoot Your vCenter HA Environment
- Patching a vCenter High Availability Environment
- Using Microsoft Clustering Service for vCenter Server on Windows High Availability
Some Hosts Are Overloaded with FT Virtual Machines
You might encounter performance problems if your cluster's hosts have an imbalanced distribution of FT
VMs.
Problem
Some hosts in the cluster might become overloaded with FT VMs, while other hosts might have unused
resources.
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.
vSphere Availability
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