Service availability during ONTAP upgrades can be optimized through planning and configuration. In many cases, upgrades can be completely nondisruptive from a client perspective.
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Considerations for services and protocols during upgrades
In general, services based on stateless protocols—such as NFSv3, FC, and iSCSI—are less susceptible to service interruptions during upgrades than session-oriented protocols—such as CIFS and NDMP.
How firmware is updated during the ONTAP upgrade
Because upgrading ONTAP includes upgrading your firmware, you do not need to update firmware manually. When you perform an ONTAP upgrade, the firmware for your cluster included with the ONTAP upgrade package is copied to each node's boot device, and the new firmware is installed automatically.
Understanding background disk firmware updates
When a node reboots and there is new disk firmware present, the affected drives are automatically and sequentially taken offline, and the node responds normally to read and write requests.