On Thu, 2 Aug 2012 14:56:38 -0700 "Yount, William D" <[email protected]> wrote: > My expectation with an active/active cluster is that the resources > are running on both servers at the same time and they are accessible > from either server simultaneously. If either server goes down, the > collocated IP address should mean that all the traffic automatically > flows to the one server that is still up. > > I am quite confused as to why there is a "process" of switching from > one node to the other. I am starting to wonder if active/active truly > means active/active.
Active/Active does indeed mean that the same resources are running on all participating nodes(*). And you can access the resources on all nodes. But when you use one "cluster ip", you can have this either on one of the nodes, then failover takes a short amount of time till its moved to the other node. Or you have several hosts answer the cluster-ips connection on a distribution-scheme. But then when one node fails, there is also a short amount of time till the other nodes recalculate the answering-scheme. So for some users or ip-connections there will be a short hang or even a disconnect/reconnect. Which isn't a problem with small http-requests but your ssh-session will fail... And the complexity of an active/active cluster are often not worth the benefits. Most setups are fine with a short outage of up to a minute. Except windows accessing samba:-( Have fun, Arnold
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