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
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.
Problem
When you select Turn On Fault Tolerance for a powered-on VM, the operation fails and you see an
Unknown error message.
Cause
This operation can fail if the host that the VM is running on has insufficient memory resources to provide
fault tolerant protection. vSphere Fault Tolerance automatically tries to allocate a full memory reservation
on the host for the VM. Overhead memory is required for fault tolerant VMs and can sometimes expand to
1 to 2 GB. If the powered-on VM is running on a host that has insufficient memory resources to
accommodate the full reservation plus the overhead memory, trying to turn on Fault Tolerance fails.
Subsequently, the Unknown error message is returned.
Solution
Choose from these solutions:
n
Free up memory resources on the host to accommodate the VM's memory reservation and the added
overhead.
n
Move the VM to a host with ample free memory resources and try again.
FT Virtual Machines not Placed or Evacuated by vSphere DRS
FT virtual machines in a cluster that is enabled with vSphere DRS do not function correctly if
Enhanced vMotion Compatibility (EVC) is currently disabled.
Problem
Because EVC is a prerequisite for using DRS with FT VMs, DRS does not place or evacuate them if EVC
has been disabled (even if it is later reenabled).
Cause
When EVC is disabled on a DRS cluster, a VM override that disables DRS on an FT VM might be added.
Even if EVC is later reenabled, this override is not canceled.
vSphere Availability
VMware, Inc. 66