2 Node Multi Site Cluster in Windows 2008R2

2 Node Multi Site Cluster in Windows 2008R2

Multi site cluster involves failover feature between sites.There are generally two things that will have to be travel between nodes: data traffic and cluster heartbeats. One thing more you have to be consider client connectivity and cluster management activity.Your replication traffic will most likely require the great
amount of bandwidth; you will need to work with your replication vendor to determine how much bandwidth is required. The last thing you need to consider is Quorum model.For a 2-node multi-site cluster configuration, the Microsoft recommended configuration is a Node and File
Share Majority quorum.

The most common cause of confusion with the Node and File Share Majority quorum is the placement of the
File Share Witness. Where should I put the server that is hosting the file share? Let’s look at the options.

Option 1 – place the file share in the primary site.

This is certainly a valid option for disaster recovery, but not so much for high availability. If the entire site fails
(including the Primary node and the file share witness) the Secondary node in the secondary site will not come into service automatically, you will need to force the quorum online manually. This is because it will be the only remaining vote in the cluster. One out of three does not make a majority! Now if you can live with a manual step being involved for recovery in the event of a disaster, then this configuration may be OK for you.

Option 2 – place the file share in the secondary site.
 

This is not such a good idea. Although it solves the problem of automatic recovery in the event of a complete
site loss, it exposes you to the risk of a false failover. Consider this…what happens if your secondary site goes down? In this case, your primary server (Node1) will go also go offline as it is now only a single node in the primary site and will no longer have a node majority. I can see no good reason to implement this configuration as there is too much risk involved.

Option 3 – place the file share witness in a 3rd geographic location

This is the preferred configuration as it allows for automatic failover in the event of a complete site loss and
eliminates any the possibility of a failure of the secondary site causing the primary node to go offline. By
having a 3rd  site host the file share witness you have eliminated any one site as a single point of failure, so now the cluster will act as you expect and automatic failover in the event of a site loss is possible. Identifying a 3rd geographic location can be challenging for some companies, but with the advent of cloud based utility
computing like Amazon EC2 and GoGrid, it is well within the reach of all companies to put a file share witness in the clouds and have the resiliency required for effective multi-site clusters. In fact, you may consider the cloud itself as your secondary data center and just failover to the cloud in the event of a disaster. I think the possibilities of cloud based computing and disaster recovery configurations are extremely enticing and in fact I plan on doing a whole blog post on a just that in the near future.