I emphasized throughout this book that the first thing we look at is contention, and not utilization. So I thought I would provide guidance on the value you should set for a contention SLA. This is not an official guidance from VMware, but a recommendation from my own experience. The actual numbers you set may not be the same as mine. You should choose numbers that you are comfortable with, and have been agreed upon by your customers (application team or business units). Not having a defined SLA can result in miscommunication with your customers or management, especially when performance impacts the business. If you do not have a number, the expectation will be by default set to the same as physical.

Once you set your SLA for contention, you should also monitor it. You might need to adjust it based on your specific environment. You should have two numbers. One is the SLA your customers agree on. The other is an internal number for your own proactive monitoring. The...