Configuring Failover Support for OpManager


Failover or redundancy support for OpManager is necessary to achieve uninterrupted service. It becomes cumbersome if the OpManger DB crashes or loses its network connectivity and not monitoring your network. Though regular backups help you recover from DB crashes, but it takes time for OpManger to resume its service. However, in the mean time your network will be left unmonitored and some other critical devices such as routers, mail servers etc. may go down and affect your business. Implementing a redundancy system helps you to overcome such failures.


Failover support requires you to configure OpManager Secondary or Standby server and keep monitoring the OpManager Primary server. Incase the Primary server fails the Standby server automatically starts monitoring the network. The transition is so quick and smooth that the end user does not feel the impact of the failure of the Primary server or the subsequent taking over by Standby. In parallely the Standby server triggers an email alert (email ID entered configured in the mail server settings) about the Primary's failure. Once the Primary server is restored back to operation the Standby server automatically goes back to standby mode.


Working Mechanism

The Primary server updates its presence with a symbolic count in the BEFailover table at a specified interval known as the HEART_BEAT_INTERVAL. With every update the count gets incremented. This count is known as LASTCOUNT. Similarly the standby server also updates the its presence by updating the LASTCOUNT in the BEFailover table.


When the Primary server fails, it fails to update the LASTCOUNT. The Standby server keeps monitoring the Primary's LASTCOUNT at a specified periodic interval known as FAIL_OVER_INTERVAL. By default the FAIL_OVER_INTERVAL value is 60 seconds. If required you can modify it in the Failover.xml file (<OpManager_Standby_home>\conf). Supposing, you have specified FAIL_OVER_INTERVAL as 50 seconds, the standby will monitor the Primary's LASTCOUNT for every 50 seconds. Every time, when the Standby server looks up the LASTCOUNT, it compares the previous and present counts. When the Primary server fails to update the LASTCOUNT, consecutive counts will be the same and the Standby assumes that the Primary server has failed and starts monitoring the network.



Installing the Primary Server
If you are already running OpManager, first upgrade to build 7260 before applying build 8000. If you installing OpManager for the first time directly install build 8000. While installing OpManger (build 8000) on the Primary server, select as Primary server in the installation wizard and complete the installation process. Start the Primary server.

         

Installing the Standby Server

While installing OpManager on the standby server,

  1. Select as Standby server mode in the installation wizard.


  2. Enter the Primary webserver host, port and login details and complete the installation. Do not start the Standby server.



Note: The Date and Time settings of the Primary and the Standby should be same.

Configuring Failover:
The procedures for configuring failover support varies according to the following cases (backend DB used):

Using MSSQL as the backend DB

If you are running OpManager with MSSQL as the backend DB, then implement clustering. Clustering refers to an array of databases in which the data are stored and have a single virtual IP. If any of the DB in the cluster environment fails the other DBs have the data thereby providing high availability of data. The Primary server sends all its data to a virtual IP and the data gets stored in multiple locations. The Standby server that takes control over the network in case the primary fails, then the standby server also sends the data to the same virtual IP.


For configuring MSSQL server clustering visit the below link published by Microsoft.
http://www.microsoft.com/technet/prodtechnol/sql/2000/maintain/failclus.mspx#EDAAC

MSSQL

For MSSQL, the Standby OpManager server can be started once the installation is completed, provided you have already configured MSSQL clustering for Primary server.


Once the Primary server fails, the Standby server assumes itself as the Primary server and starts monitoring the network. Once the Primary server is up, the Standby server goes back to its standby mode and monitors the Primary server.

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