Once you decide that server consolidation is in your future, here's how to get started:
1. Get your physical inventory up-to-date.
2. Determine how many resources are being used on all servers.
3. Prioritize each software subsystem according to business importance. Go where it makes sense first, balancing the benefits of server consolidation with the risk involved in moving a given application or business-process system.
For help with inventory and resource monitoring see:
"Firm Engineers Better Asset Management"
"MRTG Monitors What's Brewing"
"The End All of Network Performance Management"
"Design Tools Come Into Focus"