Does using AppFabric as a session state server for asp.net make it highly available?

Question

I have a 4 server asp.net farm. I want to use AppFabric as my session state server but I'm not sure if it will do what I want it to do. Some questions...

1: If some of the nodes crash, is any of the session data lost?

2: Does each server have a copy of the session data in case of failure?

The documentation states that you need to be running Windows Server 2008 Enterprise Edition or above for the "High Availability" features of AppFabric. I am running Windows Server 2008 Standard.

3: Does that mean I need the enterprise edition to have my session data stay safe if some of the nodes fail, or does AppFabric automatically keep the session data copied on all machines in case of failure?

Answer 1

I have't played much with the session state bits yet so this is based on AppFabric generally.

If you're not on Enterprise Edition, you can't use high availability :-( Essentially, in a non-HA scenario, each cache is 'tied' to a single node in your cluster, so the answer to your question is - it depends which node crashes. If it's the one that's got the cache on it then yes, you're boned.
If, however, you are in a HA environment any cache that is created withthe Secondaries option switched on, has two copies of the cache spread across the nodes so that if one goes down, the other copy picks up the load (and another secondary copy is created on another node).

There's quite a good conceptual explanation of HA for AppFabric here.