How to Configure Failover Functionality

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Summary

This Knowledgebase article provides information about how to configure failover functionality by modifying heartbeat settings.


More Information

The Primary and Secondary servers in a Neverfail pair are continuously connected via the Neverfail Channel. In absence of replication, the passive server issues heartbeats at regular intervals of time to ensure the active server is online and available. The active server can become unresponsive due to a hardware crash, lost network connection, or a power outage. When the passive server finds that the heartbeat process has failed, it can initiate a failover.

Procedure

Neverfail Heartbeat v5.3 and earlier

The number of heartbeats issued, as well as the time interval between two heartbeats, can be changed using the Neverfail Heartbeat Management Client. The default values are 3 heartbeats issued at a 20 second interval. These values should be carefully changed as they can affect the server pair’s functionality.

Example:

  • Setting the number of heartbeats to a high value will increase the time interval before a failover.  As a result, the active server might stay unavailable too long before the passive server initiates the failover process.
  • Setting the number of heartbeats to a low value for a server pair that has low channel bandwidth, may cause a split-brain syndrome. For more information about split-brain syndrome, see Knowledgebase article# 516 - Resolve Two Active Servers.

To disable automatic failovers initiated by the passive server, you can configure the 'Max Heartbeats Missed Before Failover' to all-nines.

To do this, follow the steps below:

  1. From the Neverfail Heartbeat Management Client, open the Communications -> Configuration tab.
  2. Set the field, 'Max Heartbeats Missed Before Failover', to all-nines.
  3. Click the Apply button to save the changes.

Neverfail Heartbeat v6.0 and later

The time interval for missed heartbeats can be changed using the Neverfail Heartbeat Management Client. The default value is 60 seconds. By default, if a heartbeat is missed for more than 60 seconds, the server group can initiate a failover. Adjusting the value for missed heartbeats should be carefully changed as it can affect the server group's functionality.

Example:

  • Setting the timeout value for missed heartbeats to a high value will increase the time interval before a failover.  As a result, the active server might stay unavailable too long before the passive server initiates the failover process.
  • Setting the timeout value for missed heartbeats to a low value for a server pair that has low channel bandwidth, may cause a split-brain syndrome. For more information about split-brain syndrome, see Knowledgebase article# 516 - Resolve Two Active Servers.

To disable automatic failovers initiated by the passive server, use the Failover dialog to configure options.

To do this, follow the steps below:

  1. From the Neverfail Heartbeat Management Client, select the Server: Monitoring tab.
  2. Click the Failover button.
  3. Clear the following check boxes:
    • Failover from Primary server to Secondary server if channel heartbeat is lost for failover timeout.
    • Failover from Secondary server to Primary server if channel heartbeat is lost for failover timeout.
  4. Click OK .


Applies To

All Versions


Related Information

None

KBID-794

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