264 IBM System Storage N series Hardware Guide20.1 System NDUSystem NDU is a process that takes advantage of HA pair controller technology to minimizeclient disruption during an upgrade of Data ONTAP or controller firmware.System NDU entails a series of takeover and giveback operations, These operations allowthe partner nodes to transfer the data delivery service while the controllers are upgraded.This process maintains continuous data I/O for clients/hosts.The controller for each node in the HA pair configuration is connected to both its own storageshelves and the storage shelves of its partner node. Therefore, a single node provides accessto all volumes and LUNs, even when the partner node is shut down. This configuration allowseach node of HA pair controllers to be upgraded individually to a newer version of DataONTAP or firmware. It also allows you to transparently perform hardware upgrades andmaintenance on the HA pair controller nodes.Before performing an NDU, create an NDU plan. For more information about developing anNDU plan, see the Data ONTAP 8.1 7-Mode Upgrade and Revert/Downgrade Guide at:http://www.ibm.com/support/docview.wss?uid=ssg1S700377620.1.1 Types of system NDUThere are two types of system NDUs: Major and minor: A major version system NDU is an upgrade from one major release of Data ONTAP toanother. For example, an upgrade from Data ONTAP 7.2.x to Data ONTAP 7.3.x isconsidered a major system NDU.– Major version NDU is supported ONLY when going from one release to the next insequence. There are occasionally exceptions when deemed necessary to bypass amajor release in an upgrade sequence. For example, customers are allowed tonondisruptively upgrade from 7.3 to 8.1 without having to upgrade to 8.0 as an interimstep. These exceptions are documented in Table 20-1 on page 265. A minor version system NDU is an upgrade within the same release family. For example,an upgrade from Data ONTAP 7.3.1 to Data ONTAP 7.3.2 is considered a minor systemNDU. The following are things that constitute a minor version system NDU:– No version number change to RAID, WAFL, NVLOG, FM, or SANOWN– No change to NVRAM format– No change to on-disk format– Automatic takeover must be possible while the two controllers of the HA pair arerunning different versions within the same release family20.1.2 Supported Data ONTAP upgradesSupport for system NDU differs slightly according to the protocols that are in use on thesystem. The following sections address those different protocols.Attention: Because of the complexity and individual clients environments, always see therelease notes and the upgrade guide available for your new Data ONTAP release beforeany upgrades.
