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
Networking Dierences
vSAN has its own network. If vSAN and vSphere HA are enabled for the same cluster, the HA interagent
traffic flows over this storage network rather than the management network. vSphere HA uses the
management network only if vSAN is disabled. vCenter Server chooses the appropriate network if
vSphere HA is configured on a host.
Note You can enable vSAN only if vSphere HA is disabled.
If you change the vSAN network configuration, the vSphere HA agents do not automatically pick up the
new network settings. To make changes to the vSAN network, you must take the following steps in the
vSphere Client:
1 Disable Host Monitoring for the vSphere HA cluster.
2 Make the vSAN network changes.
3 Right-click all hosts in the cluster and select Reconfigure for vSphere HA.
4 Re-enable Host Monitoring for the vSphere HA cluster.
Table 2‑2 shows the differences in vSphere HA networking whether or not vSAN is used.
Table 2‑2. vSphere HA Networking Dierences
vSAN Enabled vSAN Disabled
Network used by vSphere HA vSAN storage network Management network
Heartbeat datastores Any datastore mounted to > 1 host, but
not vSAN datastores
Any datastore mounted to > 1 host
Host declared isolated Isolation addresses not pingable and
vSAN storage network inaccessible
Isolation addresses not pingable and
management network inaccessible
Capacity Reservation Settings
When you reserve capacity for your vSphere HA cluster with an admission control policy, you must
coordinate this setting with the corresponding vSAN setting that ensures data accessibility on failures.
Specifically, the Number of Failures Tolerated setting in the vSAN rule set must not be lower than the
capacity that the vSphere HA admission control setting reserved.
For example, if the vSAN rule set allows for only two failures, the vSphere HA admission control policy
must reserve capacity that is equivalent to only one or two host failures. If you are using the Percentage
of Cluster Resources Reserved policy for a cluster that has eight hosts, you must not reserve more than
25% of the cluster resources. In the same cluster, with the Host Failures Cluster Tolerates policy, the
setting must not be higher than two hosts. If vSphere HA reserves less capacity, failover activity might be
unpredictable. Reserving too much capacity overly constrains the powering on of virtual machines and
intercluster vSphere vMotion migrations.
vSphere Availability
VMware, Inc. 27