Which upgrade method minimizes downtime when upgrading MetroCluster hardware?

A rolling upgrade is the methodology used to upgrade MetroCluster hardware components (such as controllers) non-disruptively. The process involves taking one site offline for the upgrade while the other site continues to serve data to clients. After the first site's hardware is replaced and brought back online, a switchover is performed. The second site then takes over the workload, allowing the hardware on the first site to be upgraded. This sequential, or "rolling," process ensures continuous data availability and minimizes service downtime during the hardware refresh cycle.

B. A cold upgrade requires a complete shutdown of the entire MetroCluster environment, resulting in significant service downtime.

C. A manual rebuild is a procedure for recovering from a failure, not a planned method for upgrading hardware.

D. Disk migration is a process of moving data between storage media, which may be part of an upgrade, but "rolling upgrade" describes the overall methodology.

1. NetApp, Inc. (2022). Upgrading controllers in a four-node MetroCluster configuration. TR-4742. Section: "Overview of the controller upgrade process." The document describes the non-disruptive, rolling procedure of upgrading one HA pair at a time.

2. NetApp, Inc. (2023). MetroCluster Service Guide. ONTAP 9. Section: "Overview of nondisruptive controller hardware upgrade." This section explicitly details the rolling upgrade process to ensure data services remain online.