I have been unable to find an answer to this question was hoping someone here would be able to help me.

I am currently wokring on an application and setup for a small business and I have a question about using a router for clustering.

I know that in a usual cluster setup, you have a router that goes to a load-balancer/dispatcher which then dispatches requests to the clustered servers. The problem is that this is a small business - they can't afford three servers (nor two and a load-balancer). However, the business needs fail-over as they rely on this application being up all-day long. I am wondering if the capabilities of commonly used routers today allow me to do one of the following:

(In this scenario, the router is connected to two servers)

1. Send requests to one server unless that one doesn't respond, and then automatically switch to sending requests to the other?

2. Send requests to both servers at once? i.e. duplicate the requests and send to all connected servers?

In #1, my software would handle replication/clustering of the two server's data/sessions.

Any help someone can give in this area would be greatly appreciated.

Thank you,

Robert Paris

You didnt' specify an underlying OS, hardware model, etc...but let me take astab at it.

The way clustering works is that each machine has 2 interfaces. One interface for each box is reserved for it's heartbeat, and is on a private subnet. when a cluster is created, both boxes are given a combined IP address that points to the cluster. When the heartbeat fails on one of these machines, after a certain amount of time, the other box goes active and answers the IP address requests.

You don't need load balancing.
The only thing the router is there for is to send along the IP requests to the cluster itself, and if you're not using a private switch for the heartbeat, to route that betwen the two(there are several other methods of doing this as well). All you need are two servers with 2 interfaces each(minimum) to do clustering. There are of course even ways to get around this.