One important metric displayed in the Analysis tab is the Confidence metric. During the analysis phase, performance data about each selected system is collected. This data is used to find a host with resources that match the collected data to determine a recommendation for each candidate.

The recommendation indicates how well suited, based on the collected data, a candidate is to a particular virtual machine host system. Confidence refers to the reliability of the recommendation and it is a function of the duration of the analysis. Recommendations based on longer periods of analysis – and therefore more performance data – receive a higher level of confidence.


After 24 hours of analysis, vCenter Server indicates a high level of confidence in its recommendations. However, this can be misleading if a system’s workload varies significantly over weeks or months. To ensure a high level of confidence in a recommendation, allow the duration of the analysis phase to encompass an amount of time that includes representative peaks and troughs in the systems’ workload. Analysis can run up to one month.