6.5

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 identied by the log of
update records that are saved on the passive server but not yet applied to the replicated les.
The amount of data in the passive server’s receive queue aects 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 unique Management IP address is removed from the
passive server and the shared Principal (Public) IP address is assigned. The passive server becomes active
and available to clients that were connected to the previously active server before the automatic failover
and clients 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 oine and the originally passive server is lling the active role
and 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 dier from an 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 or vSphere Client to allow the roles of
the servers to switch over the WAN.
VMware, Inc. 17
Chapter 1 Introduction