Information About High Availability
The purpose of high availability (HA) is to limit the impact of failures—both hardware and software— within a system. The Cisco NX-OS operating system is designed for high availability at the network, system, and service levels.
The following Cisco NX-OS features minimize or prevent traffic disruption if a failure occurs:
- Redundancy—Redundancy at every aspect of the software architecture.
- Isolation of processes—Isolation between software components to prevent a failure within one process disrupting other processes.
- 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—Active/standby dual supervisor configuration. The state and configuration remain constantly synchronized between two Virtual Supervisor Modules (VSMs) to provide a seamless and statefu1 switchover if a VSM failure occurs.
Cisco Nexus 1000V is made up of the following:
- Virtual Ethernet Modules (VEMs) running within virtualization servers. These VEMs are represented as modules within the VSM.
- A remote management component, such as VMware vCenter Server.
- One or two VSMs running within virtual machines (VMs).
System-Level High Availability
Cisco Nexus 1000V supports redundant VSM virtual machines—a primary and a secondary—running as an HA pair. Dual VSMs operate in an active/standby capacity in which only one VSM is active at any given time; while the other VSM acts as a standby backup. The state and configuration are constantly synchronized between two VSMs to provide a stateful switchover if the active VSM fails.
Network-Level High Availability
The Cisco Nexus 1000V HA at the network level includes port channels and Link Aggregation Control Protocol (LACP). A port channel bundles physical links into a channel group to create a single logical link that provides the aggregate bandwidth of up to eight physical links. If a member port within a port channel fails, the traffic previously carried over the failed link switches to the remaining member ports within the port channel.
Additionally, LACP allows you to configure up to 16 interfaces into a port channel. A maximum of eight interfaces can be active, and a maximum of eight interfaces can be placed in a standby state.
For additional information about port channels and LACP, see the Cisco Nexus 1000V Layer 2 Switching Configuration Guide.