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Installation Guide
12 VMware, Inc.
Figure 1-1. Failover
A failover is similar to a switchover but is used in more urgent situations, such as when the passive server
detects that the active server is no longer responding. This can occur when the active server hardware fails,
loses its network connections, or otherwise becomes unavailable. Rather than the active server gracefully
closing, the passive server determines that the active server has failed and requires no further operations. In a
failover, the passive server immediately assumes the active server role. The failover process is discussed later
in this guide.
Network Protection
vCenter Server Heartbeat proactively monitors the network by polling up to three nodes to ensure that the
active server is visible on the network. vCenter Server Heartbeat polls defined nodes around the network,
including the default gateway, the primary DNS server, and the global catalog server at regular intervals. If
all three nodes fail to respond, for example, in the case of a network card failure or a local switch failure,
vCenter Server Heartbeat can initiate a switchover, allowing the Secondary server to assume an identical
network identity as the Primary server.
Application Protection
vCenter Server Heartbeat running on the active server locally monitors the applications and services it has
been configured to protect (through the use of plug-ins) to verify that protected applications are operational
and not in an unresponsive or stopped state. This level of monitoring is fundamental in ensuring that
applications remain available to users.
If a protected application fails, vCenter Server Heartbeat first tries to restart the application on the active server
(1) in Figure 1-2.
If the application does not successfully restart, vCenter Server Heartbeat initiates a switchover (2) in
Figure 1-2. Refer to “vCenter Server Heartbeat Switchover and Failover Processes” on page 15 for further
information about the switchover process.