How to Prevent Neverfail Engine Failover to an Isolated Passive Server

How to Prevent Neverfail Engine Failover to an Isolated Passive Server


This Knowledgebase article provides the procedure to configure Neverfail Continuity Engine to prevent failover to an isolated passive server.

More Information

With the Primary (active) and Secondary (passive) server configured for High Availability, should passive server become isolated due to communications failure with the active server long enough to initiate a failover, the failover may result in a Split-brain scenario.

To prevent a Split-brain scenario from occurring, create a Pre-start task to verify communications between the Secondary (newly active) server and a destination that is external to the local network. 

To create a user defined Pre-start task:

  1. Create a script file consisting of the following:

    Note: Neverfail recommends the script file be located in a protect folder to ensure identical scripts are located on both the Primary and Secondary servers.

    ping | find "TTL" || net stop nfserverr2 && net start nfserverr2

  2. Navigate to the Tasks page of the Engine Management Service user interface.
  3. Click Add at the lower right of the pane. The Add Task dialog appears.
  4. Type a Name for the task into the text box.
  5. Select the Task Type from the drop-down list. The Task type selected should be Pre-Start.
  6. In the Command text box, type in the path or browse to the script file for the task to perform.

    When the Command entry requires specific user credentials, you must select that user from the Run As drop-down list.
  7. Select from the options presented in the Run As drop-down list (typically includes local and administrator accounts).
  8. Click OK to add the task. 

Applies To

Neverfail Continuity Engine

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