High Availability and Redundancy

anubhuti123 · ‎12-17-2008

Can anyone tell the differnce between high availability and redundancy of the network.

Joseph W. Doherty · ‎12-17-2008

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High availability is the goal or objective, redundancy is one method.

Redundancy might imply surplus of resources, but high availability might also be provided by multiple resources yet without a surplus capacity. If loss of resources degrades service you still have availability.

High availability is often quoted as a percentage of actual up-time vs. planned up-time. "Five nines", 99.999%, is a popular goal. More information on hihg availability can be read in this Wiki article, http://en.wikipedia.org/wiki/High_availability.

Jon Marshall · ‎12-17-2008

Redundancy is one of the factors that leads to high availability. So if you have redundant switch links, redundant supervisors in your modular switches etc. then the availability of your network should not be affected if one of the links fails or one of the supervisors fails.

Jon

RobinCruz · ‎01-13-2009

I searched and found this thread and thought maybe those listed might be able to help. How can one configure a network to have redundant links to a single NIC or MAC address? This would be called fault tolerant so that if one link failed the other link would still provide data. This would be 2 100BaseT links from a router/switch to a single NIC/IP address.

Would duplicate data be sent and the receiver somehow select one or would the router reconverge to the redundant link by sensing a link failure and reconveging to the backup?

Any thoughts or literature you might refer me to so that I could understand how to do this or if it can be done?

Thanks for any tips