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
If DRS does not place or evacuate FT VMs in the cluster, check the VMs for a VM override that is
disabling DRS. If you find one, remove the override that is disabling DRS.
Note For more information on how to edit or delete VM overrides, see vSphere Resource Management.
Fault Tolerant Virtual Machine Failovers
A Primary or Secondary VM can fail over even though its ESXi host has not crashed. In such cases,
virtual machine execution is not interrupted, but redundancy is temporarily lost. To avoid this type of
failover, be aware of some of the situations when it can occur and take steps to avoid them.
Partial Hardware Failure Related to Storage
This problem can arise when access to storage is slow or down for one of the hosts. When this occurs
there are many storage errors listed in the VMkernel log. To resolve this problem you must address your
storage-related problems.
Partial Hardware Failure Related to Network
If the logging NIC is not functioning or connections to other hosts through that NIC are down, this can
trigger a fault tolerant virtual machine to be failed over so that redundancy can be reestablished. To avoid
this problem, dedicate a separate NIC each for vMotion and FT logging traffic and perform vMotion
migrations only when the virtual machines are less active.
Insucient Bandwidth on the Logging NIC Network
This can happen because of too many fault tolerant virtual machines being on a host. To resolve this
problem, more broadly distribute pairs of fault tolerant virtual machines across different hosts.
Use a10-Gbit logging network for FT and verify that the network is low latency.
vMotion Failures Due to Virtual Machine Activity Level
If the vMotion migration of a fault tolerant virtual machine fails, the virtual machine might need to be failed
over. Usually, this occurs when the virtual machine is too active for the migration to be completed with
only minimal disruption to the activity. To avoid this problem, perform vMotion migrations only when the
virtual machines are less active.
Too Much Activity on VMFS Volume Can Lead to Virtual Machine Failovers
When a number of file system locking operations, virtual machine power ons, power offs, or vMotion
migrations occur on a single VMFS volume, this can trigger fault tolerant virtual machines to be failed
over. A symptom that this might be occurring is receiving many warnings about SCSI reservations in the
VMkernel log. To resolve this problem, reduce the number of file system operations or ensure that the
fault tolerant virtual machine is on a VMFS volume that does not have an abundance of other virtual
machines that are regularly being powered on, powered off, or migrated using vMotion.
vSphere Availability
VMware, Inc. 67