6.5

Table Of Contents
vCenter Server Heartbeat intercepts all le system I/O operations on the active server. If the intercepted write
and update operations are within the protected set, these are placed in a queue on the active server referred
to as the active servers “Send Queue”, pending transmission to the passive server. Each request is numbered
to maintain its order in the queue. With the request in the active servers send queue, vCenter Server Heartbeat
allows the disk I/O to continue with the requested disk operation.
If the channel is connected, the active servers send queue is transferred to the passive server, which places all
the requests in the passive servers “Receive Queue”. The passive server conrms the changes were logged by
sending the active server an acknowledgment. The active server then clears the data from its queue.
Figure 1- 3. Apply Process
The apply process running on the passive servers receive queue applies all updates in strict sequence,
duplicating an identical set of le operations on the passive server as illustrated in Figure 1-3.
vCenter Server Heartbeat Communications
The VMware Channel is a crucial component of the setup and can be congured in a number of ways.
vCenter Server Heartbeat supports installation using either multiple network interface connections (NICs), (1
congured for the VMware Channel) and (1 congured with the Principal(Public) and Management IP
addresses), or a single NIC congured with the VMware Channel IP, Principal (Public) IP, and Management
IP. Both the Primary and Secondary servers must have the same number of NICs. The Principal (Public) IP
address provides client access and the Management IP address provides administrative access, while the
VMware Channel provides for data transfer and control.
A second pair of NICs for the VMware Channel can be used to provide a degree of redundancy. In this
conguration, the VMware Channel has a dual channel if more than one dedicated NIC is provided for the
VMware Channel on each server. To provide added resilience, the communications for the second channel
should be completely independent from the rst channel. They should not share any switches, virtual switches,
routers or the same WAN connection.
VMware, Inc. 13
Chapter 1 Introduction