Virtualising and consolidating servers can bring multiple benefits to corporate data centres: smaller server footprints, lower heating and cooling costs, less cabling and more efficient management of resources. But there are downsides to consolidating and virtualising servers that companies need to quantify before jumping on the consolidation band wagon.

Software Licensing. Larger servers include more CPUs that each has more processing power. However this can translate into increased software licensing costs. I just spoke to one company that found out too late that their software licensing costs were tied to the number of CPUs and their increased processing power in their new hardware. This surprise offset many of the financial benefits that consolidation was supposed to provide and may even negate them.

Complexity. "One physical server = one application" is an equation that anyone can understand and manage. However consolidation changes the equation to "One physical server = X number of applications and/or operating systems". This makes consolidated environments as complex as having hundreds of servers each supporting its own application. As companies consolidate, they need to ensure that they have processes in place that manage the sharing of server processors, memory and network bandwidth.

Single Point of Failure. No company likes to contemplate the possibility human error. But pull the wrong cable, flip the wrong switch or "fat finger" an entry and suddenly putting all of your eggs in one basket does not seem like such a great idea. Robust disaster recovery plan and server configurations that facilitate fast, easy failovers should be considered mandatory.

Server virtualisation and consolidations clearly bring key cost savings and environmental benefits to corporate data centres. But it is equally important to understand what pitfalls that server virtualisation and consolidations introduce so companies can avoid falling into them.

Jerome Wendt is the president and lead analyst at DCIG Inc. You may read his blogs at www.dciginc.com.