What is the impact of a nondisruptive update on a Cisco MOS 9000 Series Modular Switch?

A nondisruptive update, or In-Service Software Upgrade (ISSU), on a Cisco MDS switch involves loading a new software image onto the standby supervisor module while the active supervisor continues to forward traffic. A key part of this process is the system managing its resources to accommodate the new image. The system must allocate memory (RAM) and check for sufficient bootflash space to load and run the new software on the standby supervisor before initiating a switchover. This action of managing and assigning resources for the new image is an intrinsic part of the update process itself.

A. The upgrade being aborted due to pending CFS commits is the result of a failed pre-upgrade check, not an impact of the update process itself.
B. An ISSU process is blocked and will not continue if a critical fabric operation like a zone merge is in progress; it does not run uninterrupted.
C. The system BIOS (or bootloader) is typically updated automatically as part of the install all process if required, not as a separate manual step after completion.

1. Cisco, Cisco MDS 9000 Series NX-OS Software Upgrade and Downgrade Guide, Release 8.x, Chapter: "About In-Service Software Upgrades", Section: "ISSU Process". The guide describes the process: "The new software is loaded on the standby supervisor... The standby supervisor is brought up with the new software." This loading process inherently requires system resource allocation.

2. Cisco, Cisco MDS 9000 Family NX-OS Fundamentals Configuration Guide, Chapter: "In-Service Software Upgrades". This guide details the ISSU process, including the step of loading the new image onto the standby supervisor, which implies the allocation of system resources like memory and storage space.