Installation guide

VMware, Inc. 15
Chapter 1 Introduction
Figure 1-6. Failover
During the automatic failover, the passive server performs the following steps:
1 Apply any intercepted updates currently in the passive server’s receive queue as identified by the log of
update records that are saved on the passive server but not yet applied to the replicated files.
The amount of data in the passive server’s receive queue affects the time required to complete the failover
process. If the passive server’s receive queue is long, the system must wait for all updates to the passive
server to complete before the rest of the process can take place. An update record can be applied only if
all earlier update records are applied, and the completion status for the update is in the passive server’s
receive queue. When no more update records can be applied, any update records that cannot be applied
are discarded.
2 Switch mode of operation from passive to active.
This enables the public identity of the server. The active and passive servers both use the same Principal
(Public) IP address. This Principal (Public) IP address can be enabled only on one system at anytime.
When the public identity is enabled, any clients previously connected to the server before the automatic
failover are able to reconnect.
3 Start intercepting updates to protected data. Any updates to the protected data are saved in the send
queue on the local server.
4 Start all protected applications. The applications use the replicated application data to recover, and then
accept re-connections from any clients. Any updates that the applications make to the protected data are
intercepted and logged.
At this point, the originally active server is offline and the originally passive server is filling the active role
and is running the protected applications. Any updates that completed before the failover are retained.
Application clients can reconnect to the application and continue running as before.
Managed Failover
Managed failover is similar to automatic failover in that the passive server automatically determines that the
active server has failed and can warn the system administrator about the failure; but no failover actually occurs
until the system administrator manually triggers this operation.
Automatic Switchover and Failover in a WAN Environment
Automatic switchover and failover in a WAN environment differ from a automatic switchover and failover in
a LAN environment due to the nature of the WAN connection. In a WAN environment, automatic switchover
and failover are disabled by default in the event that the WAN connection is lost.
Should a condition arise that would normally trigger an automatic switchover or failover, the administrator
will receive vCenter Server Heartbeat alerts. The administrator must manually click the Make Active button
on the Server: Summary page of the vCenter Server Heartbeat Console to allow the roles of the servers to
switch over the WAN.