6.5

vCenter Server Heartbeat provides all ve protection levels continuously, ensuring all facets of the user
environment are maintained at all times, and that vCenter Server continues to operate through as many failure
scenarios as possible.
Server Protection
vCenter Server Heartbeat provides continuous availability to end users through a hardware failure scenario
or operating system crash and ensures users are provided with a replica server and its IP address on the failure
of the production server.
Two instances of vCenter Server Heartbeat regularly send “I’m alive” messages and message acknowledgments
to one another over a dedicated network connection referred to as the “VMware Channel” to detect interruptions
in responsiveness. If the passive server detects that this monitoring process (referred to as the “Heartbeat”)
has failed, it initiates a failover as illustrated in Figure 1-1.
Figure 1- 1. Failover
A failover occurs 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 in detail later in this guide.
Network Protection
vCenter Server Heartbeat proactively monitors the network by polling up to three predened nodes to ensure
that the active server is visible on the network. vCenter Server Heartbeat polls by default the primary DNS
server, the default gateway, and the global catalog server at regular intervals. If all three nodes fail to respond,
for example in the case of a network card or local switch failure, vCenter Server Heartbeat can initiate a
switchover, allowing the Secondary server to assume the active role and service clients.
Application Protection
vCenter Server Heartbeat running on the active server locally monitors vCenter Server and its services (through
the use of plug-ins) to verify that vCenter Server is operational and not in an unresponsive or stopped state.
This level of monitoring is fundamental in ensuring that vCenter Server remains available to users.
VMware, Inc. 11
Chapter 1 Introduction