Nature of Statistics in vCenter Server

vCenter Server supplies statistics of several types.

The guest operating system computes statistics either as rates, such as CPU cycles per second, or as snapshots of size, such as KB used for storage. Statistics stored as size snapshots are collected at the end of their sample periods. Statistics stored as rates are computed as averages of values sampled frequently during each sample period.

When you query the statistics database, the units are not returned with the data, but you can determine the units for any metric by requesting metadata for the metric with the get() method.