Product Documentation

Configuring Fail-Safe Mode

Sep 01, 2016

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.

Table 1. Fail-Safe Mode Cases
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 configuration utility

  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.