Specifications

Reference Guide
14 VMware, Inc.
Data Protection
You can configure vCenter Server Heartbeat to protect the application environment. All data files that users or
the applications require in the application environment are made available should a failure occur. After
installation, vCenter Server Heartbeat configures itself to protect files, folders, and registry settings for
vCenter Server on the active server by mirroring them in real time to the passive server. This means that if a
failover occurs, all the files that were protected on the failed server are available to users after the failover,
hosted on the Secondary server.
vCenter Server Heartbeat intercepts all file 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 server (unsafe) queue, pending transmission to the passive server. Each request is numbered to
maintain its order in the queue.
With the request in the active server (unsafe) queue, vCenter Server Heartbeat allows the disk I/O to continue
with the requested disk operation.
If the channel is connected, the active server (unsafe) queue is transferred to the passive server, which places
all the requests in the passive server (safe) queue. The passive server confirms the changes were logged by
sending the active server an acknowledgement. The active server clears the data from its queue.
Figure 1-3. Apply Process
The apply process running on the passive server (safe) queue applies all updates in strict sequence, duplicating
an identical set of file operations on the passive server as illustrated in Figure 1-3.
Communications
The VMware Channel is a crucial component of the setup and can be configured in a number of ways.
Both the Primary and Secondary servers must have two or more network interface connections (NICs).
The Principal (Public) network requires one NIC. The VMware Channel uses a separate NIC for the private
connection between the servers used for control and data transfer between the pair of servers.
A second pair of NICs can be used to provide a degree of redundancy for the VMware Channel. In this
configuration, 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
must be completely independent from the first channel. They must not share any switches, virtual switches,
routers or the same WAN connection.