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
Networks Used for vSphere HA Communications
To identify which network operations might disrupt the functioning of vSphere HA, you must know which
management networks are being used for heart beating and other vSphere HA communications.
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On legacy ESX hosts in the cluster, vSphere HA communications travel over all networks that are
designated as service console networks. VMkernel networks are not used by these hosts for vSphere
HA communications. To contain vSphere HA traffic to a subset of the ESX console networks, use the
allowedNetworks advanced option.
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On ESXi hosts in the cluster, vSphere HA communications, by default, travel over VMkernel
networks. With an ESXi host, if you want to use a network other than the one vCenter Server uses to
communicate with the host for vSphere HA, you must explicitly enable the Management traffic check
box.
To keep vSphere HA agent traffic on the networks you have specified, configure hosts so vmkNICs used
by vSphere HA do not share subnets with vmkNICs used for other purposes. vSphere HA agents send
packets using any pNIC that is associated with a given subnet when there is also at least one vmkNIC
configured for vSphere HA management traffic. Therefore, to ensure network flow separation, the
vmkNICs used by vSphere HA and by other features must be on different subnets.
Network Isolation Addresses
A network isolation address is an IP address that is pinged to determine whether a host is isolated from
the network. This address is pinged only when a host has stopped receiving heartbeats from all other
hosts in the cluster. If a host can ping its network isolation address, the host is not network isolated, and
the other hosts in the cluster have either failed or are network partitioned. However, if the host cannot
ping its isolation address, it is likely that the host has become isolated from the network and no failover
action is taken.
By default, the network isolation address is the default gateway for the host. Only one default gateway is
specified, regardless of how many management networks have been defined. Use the
das.isolationaddress[...] advanced option to add isolation addresses for additional networks. See
vSphere HA Advanced Options.
Network Path Redundancy
Network path redundancy between cluster nodes is important for vSphere HA reliability. A single
management network ends up being a single point of failure and can result in failovers although only the
network has failed. If you have only one management network, any failure between the host and the
cluster can cause an unnecessary (or false) failover activity if heartbeat datastore connectivity is not
retained during the networking failure. Possible failures include NIC failures, network cable failures,
network cable removal, and switch resets. Consider these possible sources of failure between hosts and
try to minimize them, typically by providing network redundancy.
vSphere Availability
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