6.5.1
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
- 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
- Index
For virtual machines with Fault Tolerance enabled, you might use ISO images that are accessible only to the
Primary VM. In such a case, the Primary VM can access the ISO, but if a failover occurs, the CD-ROM
reports errors as if there is no media. This situation might be acceptable if the CD-ROM is being used for a
temporary, noncritical operation such as a patch.
Avoid Network Partitions
A network partition occurs when a vSphere HA cluster has a management network failure that isolates
some of the hosts from vCenter Server and from one another. See “Network Partitions,” on page 17. When a
partition occurs, Fault Tolerance protection might be degraded.
In a partitioned vSphere HA cluster using Fault Tolerance, the Primary VM (or its Secondary VM) could end
up in a partition managed by a master host that is not responsible for the virtual machine. When a failover is
needed, a Secondary VM is restarted only if the Primary VM was in a partition managed by the master host
responsible for it.
To ensure that your management network is less likely to have a failure that leads to a network partition,
follow the recommendations in “Best Practices for Networking,” on page 38.
Using vSAN Datastores
vSphere Fault Tolerance can use vSAN datastores, but you must observe the following restrictions:
n
A mix of vSAN and other types of datastores is not supported for both Primary VMs and Secondary
VMs.
n
vSAN metro clusters are not supported with FT.
To increase performance and reliability when using FT with vSAN, the following conditions are also
recommended.
n
vSAN and FT should use separate networks.
n
Keep Primary and Secondary VMs in separate vSAN fault domains.
Legacy Fault Tolerance
By default, vSphere Fault Tolerance can accommodate SMP virtual machines with up to four vCPUs. If your
virtual machine has only a single vCPU, however, you can use legacy FT instead for backward compatibility.
Unless legacy FT is technically necessary, avoid using it.
To use legacy Fault Tolerance, you must congure an advanced option for the virtual machine. After you
complete this conguration, the legacy FT VM is dierent in some ways from other vSphere FT VMs.
Differences for VMs That Use Legacy FT
VMs that use vSphere FT and VMs that use legacy FT dier in several ways.
Table 3‑2. Differences Between Legacy FT and vSphere FT
Legacy FT vSphere FT
Extended Page Tables/Rapid
Virtualization Indexing (EPT/RVI)
Not supported Required
IPv6 Not supported for legacy FT logging
NICs.
Supported for vSphere FT-logging
NICs.
DRS Fully supported for initial placement,
load balancing, and maintenance
mode support.
Only power on placement of
Secondary VM and maintenance mode
are supported.
vStorage APIs - Data Protection
backups
Not supported Supported
Chapter 3 Providing Fault Tolerance for Virtual Machines
VMware, Inc. 53