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
The largest host is H1 and if it fails, six slots remain in the cluster, which is sufficient for all five of the
powered-on virtual machines. If both H1 and H2 fail, only three slots remain, which is insufficient.
Therefore, the Current Failover Capacity is one.
The cluster has one available slot (the six slots on H2 and H3 minus the five used slots).
Dedicated Failover Hosts Admission Control
You can configure vSphere HA to designate specific hosts as the failover hosts.
With dedicated failover hosts admission control, when a host fails, vSphere HA attempts to restart its
virtual machines on any of the specified failover hosts. If restarting the virtual machines is not possible, for
example the failover hosts have failed or have insufficient resources, then vSphere HA attempts to restart
those virtual machines on other hosts in the cluster.
To ensure that spare capacity is available on a failover host, you are prevented from powering on virtual
machines or using vMotion to migrate virtual machines to a failover host. Also, DRS does not use a
failover host for load balancing.
Note If you use dedicated failover hosts admission control and designate multiple failover hosts, DRS
does not attempt to enforce VM-VM affinity rules for virtual machines that are running on failover hosts.
vSphere HA Interoperability
vSphere HA can interoperate with many other features, such as DRS and vSAN.
Before configuring vSphere HA, you should be aware of the limitations of its interoperability with these
other features or products.
Using vSphere HA with vSAN
You can use vSAN as the shared storage for a vSphere HA cluster. If enabled, vSAN aggregates the
specified local storage disks available on the hosts into a single datastore shared by all hosts.
To use vSphere HA with vSAN, you must be aware of certain considerations and limitations for the
interoperability of these two features.
For information about vSAN, see Administering VMware vSAN.
Note You can use vSphere HA with vSAN stretched clusters.
ESXi Host Requirements
You can use vSAN with a vSphere HA cluster only if the following conditions are met:
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All the cluster's ESXi hosts must be version 5.5 or later.
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The cluster must have a minimum of three ESXi hosts.
vSphere Availability
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