When it comes to clustering.. doesn't matter if it is MySQL, MS SQL Server, MS Exchange or a big bad Beowulf Cluster you need an independent switch for the cluster. Here is why, There is so much traffic to and from the nodes, and on the network that it will slow down your network, and the cluster. A cluster has more communication on it than just serving your data, it has management information as well. Our typical setup for a cluster (OS and Job independent) is usually a 10/100/1000 switch, noting fancy like a managed switch but quality (not putting in a $40 switch). We also do not allow switches to be over 75% used, if a 12 port switch has more than 9 ports used we replace it with a 24 port. Typically we also use a rack to house all the clustered boxes with nothing else not required for the cluster in there. The exception is when it is only 2 boxes in the cluster then we just rack them next to each other and instead of a switch we use a fiber connection between the two boxes. We set up a lot of clusters for various Operating systems and servers and these are our general rules of set up. These simple rules have never let us down when it comes to clustering. When cluster traffic is running outside the cluster you are asking for network performance issues.
