IMG 1010 - GCEMS_Redundancy
Overview:
As of software 10.5.1 the GCEMS application supports having a redundant pair. The GCEMS application supports having a Primary GCEMS application running on one server and a Secondary GCEMS application running on a second host. GCEMS redundancy increases reliability to the IMG network by giving the system a backup or fail safe GCEMS in the event the Primary GCEMS fails. A switchover occurs only when there is a failure. There is no mechanism built into ClientView that allows a user to execute a manual switchover. The only way to force a manual switchover would be to power down the Primary Host and allow the Secondary Host with the secondary managers to take over.
GCEMS Redundancy is provided by maintaining communication between both servers. If redundancy is deployed over an unstable network, consider utilizing IMG 1010 - GCEMS redundancy - Utilizing Bonding. Any time the GCEMS applications on both GCEMS servers become Active due to loss of network connectivity, network redundancy is compromised.
Below are a few bulleted items describing when a switchover would occur. It is important to recognize that the Primary Host does not always have the active processes on. It is also important to know that there is a difference between the Primary and Secondary Host and the active and standby processes. An active process can reside on either the primary or secondary host as well as the standby process can reside on either the primary or secondary host. Refer to the Diagram below.
Example 1:
In diagram above initially GateManagerA, GateManagerB, DataManagerA, and DataManagerB are all connected to CommManagerA. CommManager A in active state is connected to IP cloud which is then connected to IMG's. CommManagerB is in standby state. No information is being passed from CommManager B to the IMG's.
If CommManagerA goes down all the processes switch to CommManagerB. CommManagerB becomes the active and CommManagerA becomes the standby. See diagram below.
Example 2:
GateManager and DataManager are considered a pair. If either one goes down then they both will switchover as a pair. For example if GateManagerA went down you would lose the GateManagerA and DataManagerA. In this scenario the active GateManagerA, DataManagerA, and CommManagerA would switch over. GateManagerB, DataManagerB, and CommManagerB would become the active. GateManagerA, DataManagerA, and CommManagerA would become the standby when they came back online.
There are other scenarios/failures that could occur which are not explained. The information to keep in mind is at any time there will be an active GateManager/DataManager pair communicating with an active CommManager which is communicating with the IMG network. Also, after a failure, all processes will reboot themselves and come up as standby processes ready to take over in the event of an active process failure.
Related Topics:
IMG 1010 - Installing GCEMS Software