Grass Valley iControl V.4.43 - Manual (Page 588)

Backup and Redundancy
Manual Takeovers
578
Manual Takeovers
Manual Takeovers have an n+m redundancy scheme. That is, iControl doesn’t limit the
number of Main Application Servers. Likewise, iControl doesn’t limit the number of
Application Servers acting in a Backup capacity. All of the Backups are available to manually
take over the services and identities of any of the Mains.
For example, consider two Main (online) Application Servers plus one Backup Application
Server. The Backup is in a standby state and doesn’t run any processes used in normal
operation. To address the GSM as a single point-of-failure problem or GSM load balancing, we
may want to run two GSMs. GSM duties are thus load-balanced between the two Mains. When
an operator initiates a Manual Takeover from one of the Mains to the Backup, that portion of
the GSM duties being handled by the taken-over Main is switched to the Backup along with all
other services of this Application Server and its identity.
A Backup Application Server replicates the configuration data and identities of the n
Application Servers. From Webmin, a list of replication profiles can be specified. The default
replication frequency is 24 hours. This means that in the case of an Application Server failure,
any changes performed to the Application Server profile in the previous 24 hours could be
lost.
Auto-failovers
Auto-failovers have an n+1 redundancy scheme. That is, iControl doesn’t limit the number of
Main Application Servers. However, iControl does limit the number of Application Servers
acting in a Backup capacity to only one. When two or more Application Servers are configured
as a Redundancy Group in iControl’s Webmin, any one of several conditions can trigger an
Auto-failover of service from a Main Application Server to the Backup Application Server. In
such cases, the Backup assumes the full role and identity of the original (including its
IP address if the Take over the main IP address after failover check box is selected), and
becomes the new Main. This process does not require user intervention except in the initial
Redundancy Group configuration and when performing failover recovery tasks such as
Reverse Takeovers or Replace operations.
IMPORTANT: System behavior
You must configure at least one Application Server in every Redundancy Group
in the role of Backup and in a standby state in order for Auto-failovers and
Manual Takeovers to succeed.
See also
For more information about:
• Manual Takeovers, see "Configuring and Managing Application Server Redundancy" , on
page 588
• Redundancy Groups, see page 577