Product Documentation

Configuring fail-safe mode

In an HA configuration, fail-safe mode ensures that one node is always primary when both nodes fail the health check. This is to ensure that when a node is only partially available, backup methods are enabled to handle traffic as best as possible. The HA fail-safe mode is configured independently on each node.

The following table shows some of the fail-safe cases. The NOT_UP state means that the node failed the health check yet it is partially available. The UP state means that the node passed the health check.

Node A (Primary) Health State Node B (Secondary) Health State Default HA Behavior Fail-Safe Enabled HA Behavior Description
NOT_UP(failed last) NOT_UP (failed first) A (Secondary), B (Secondary) A (Primary), B (Secondary) If both nodes fail, one after the other, the node that was the last primary remains primary.
NOT_UP (failed first) NOT_UP(failed last) A (Secondary), B (Secondary) A(Secondary), B(Primary) If both nodes fail, one after the other, the node that was the last primary remains primary.
UP UP A (Primary), B (Secondary) A (Primary), B (Secondary) If both nodes pass the health check, no change in behavior with fail-safe enabled.
UP NOT_UP A(Primary), B(Secondary) A (Primary), B (Secondary) If only the secondary node fails, no change in behavior with fail-safe enabled.
NOT_UP UP A(Secondary), B(Primary) A(Secondary), B(Primary) If only the primary fails, no change in behavior with fail-safe enabled.
NOT_UP UP (STAYSECONDARY) A (Secondary), B (Secondary) A (Primary), B (Secondary) If the secondary is configured as STAYSECONDARY, the primary remains primary even if it fails.

To enable fail-safe mode by using the command line interface

At the command prompt, type:

set HA node [-failSafe ( **ON** | **OFF** )]

Example

set ha node -failsafe ON

To enable fail-safe mode by using the GUI

  1. Navigate to System > High Availability and, on the Nodes tab, open the node.
  2. Under Fail-Safe Mode, select the Maintain one Primary node even when both nodes are unhealthy option.

Configuring fail-safe mode