HA policy and how it affects takeover and giveback operations

ONTAP automatically assigns an HA policy of CFO or SFO to an aggregate that determines how storage failover operations (takeover and giveback) occur for the aggregate and its volumes.

HA policy is assigned to and required by each aggregate on the system. The two options, CFO (controller failover), and SFO (storage failover), determine the aggregate control sequence ONTAP uses during storage failover and giveback operations.

Although the terms CFO and SFO are sometimes used informally to refer to storage failover (takeover and giveback) operations, they actually represent the HA policy assigned to the aggregates. For example, the terms SFO aggregate or CFO aggregate simply refer to the aggregate's HA policy assignment.

• Aggregates created on ONTAP systems (except for the root aggregate containing the root volume) have an HA policy of SFO.

  Manually initiated takeover is optimized for performance by relocating SFO (non-root) aggregates serially to the partner prior to takeover. During the giveback process, aggregates are given back serially after the taken-over system boots and the management applications come online, enabling the node to receive its aggregates.

• Because aggregate relocation operations entail reassigning aggregate disk ownership and shifting control from a node to its partner, only aggregates with an HA policy of SFO are eligible for aggregate relocation.
• The root aggregate always has an HA policy of CFO and is given back at the start of the giveback operation since this is necessary to allow the taken-over system to boot.

  All other aggregates are given back serially after the taken-over system completes the boot process and the management applications come online, enabling the node to receive its aggregates.