How automatic takeover and giveback work

The automatic takeover and automatic giveback operations can work together to reduce and avoid client outages. They occur by default in the case of a panic or reboot, or if the cluster contains only a single HA pair. However, these operations require specific configuration for some other cases.

With the default settings, if one node in the HA pair panics or reboots, the partner node automatically takes over and then automatically gives back storage when the affected node reboots. This returns the HA pair to a normal operating state.

The automatic giveback occurs by default after a panic or a reboot. You can also configure the system to perform an automatic giveback in cases other than a panic or a reboot. However, because each of the options controls different aspects of automatic giveback, you must configure them independently.

Although you can also set the system to always attempt an automatic giveback (for cases other than a panic or a reboot), you should do so with caution:

The automatic giveback causes a second unscheduled interruption (after the automatic takeover).
Depending on your client configurations, you might want to initiate the giveback manually to plan when this second interruption occurs.
The takeover might have been due to a hardware problem that can recur without additional diagnosis, leading to additional takeovers and givebacks.

Note: Automatic giveback is enabled by default if the cluster contains only a single HA pair. Automatic giveback is disabled by default during nondisruptive ONTAP upgrades.

Before performing the automatic giveback (regardless of what triggered it), the partner node waits for a fixed amount of time as controlled by the -delay-seconds parameter of the storage failover modify command. The default delay is 600 seconds. By delaying the giveback, the process results in two brief outages:

One outage during the takeover operation
One outage during the giveback operation

This process avoids a single, prolonged outage that includes:

The time for the takeover operation
The time it takes for the taken-over node to boot up to the point at which it is ready for the giveback
The time for the giveback operation

If the automatic giveback fails for any of the non-root aggregates, the system automatically makes two additional attempts to complete the giveback.