282 IBM System Storage N series Hardware Guide20.1 System NDUSystem NDU is a process that uses HA pair controller technology to minimize client disruptionduring 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 and hosts.The controller for each node in the HA pair configuration is connected to 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 an NDU is performed, create an NDU plan. For more information about developing anNDU plan, see the Data ONTAP 8.1 7-Mode Upgrade and Revert/Downgrade Guide, which isavailable at this website:http://www.ibm.com/support/docview.wss?uid=ssg1S700377620.1.1 Types of system NDUThe following types of system NDUs are available: MajorA 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 a majorrelease in an upgrade sequence. For example, customers are allowed to nondisruptivelyupgrade from 7.3 to 8.1 without having to upgrade to 8.0 as an interim step. Theseexceptions are shown in Table 20-1 on page 283. MinorA 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 characteristics 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 familyAttention: Because of the complexity and individual clients environments, always see therelease notes and the upgrade guide that is available for your new Data ONTAP releasebefore any upgrades.
