High Availability and Redundancy Guide

To prevent or minimize traffic disruption during hardware or software failures, Cisco NX-OS has these features:

• Redundancy—Cisco NX-OS HA provides physical and software redundancy at every component level,
  spanning across the physical, environmental, power, and system software aspects of its architecture.
• Isolation of planes and processes—Cisco NX-OS HA provides isolation between control and data
  forwarding planes within the device and between software components so that a failure within one plane
  or process does not disrupt others.
• Restartability—Most system functions and services are isolated so that they can be restarted independently
  after a failure while other services continue to run. In addition, most system services can perform stateful
  restarts, which allow the service to resume operations transparently to other services.
• Supervisor stateful switchover—The Cisco Nexus 9504, 9508, and 9516 chassis support an active and
  standby dual supervisor configuration. State and configuration remain constantly synchronized between
  the two supervisor modules to provide seamless and stateful switchover in the event of a supervisor
  module failure.
• Nondisruptive upgrades—Cisco NX-OS supports the in-service software upgrade (ISSU) feature, which
  allows you to upgrade the device software while the switch continues to forward traffic. ISSU reduces
  or eliminates the downtime typically caused by software upgrades.

For more information, see the Cisco Nexus 9000 Series NX-OS High Availability and Redundancy Guide.