Each data counter includes several attributes that are used to determine the statistical value collected. See the vSphere API Reference for a complete list and description of supported counters.
Table 1.
Data Counter Attributes
Attribute 
Description 
Unit of Measurement 
Standard in which the statistic quantity is measured.
Kilobytes (KB) – 1024 bytes
Kilobytes per second (KBps) – 1024 bytes per second
Kilobits (kb) – 1000 bits
Kilobits per second (kbps) – 1000 bits per second
Megabytes (MB)
Megabytes per second (MBps)
Megabits (Mb), megabits per second (Mbps)
Megahertz (MHz)
Microseconds (µs)
Milliseconds (ms)
Number (#)
Percent (%)
Seconds (s)

Description 
Text description of the data counter. 
Statistics Type 
Measurement used during the statistics interval. Related to the unit of measurement.
Rate – Value over the current statistics interval
Delta – Change from previous statistics interval.
Absolute – Absolute value (independent of the statistics interval).

Rollup Type 
Calculation method used during the statistics interval to roll up data. Determines the type of statistical values that are returned for the counter.
Average – Data collected during the interval is aggregated and averaged.
Minimum – The minimum value is rolled up.
Maximum – The maximum value is rolled up. The Minimum and Maximum values are collected and displayed only in statistics level 4. Minimum and maximum rollup types are used to capture peaks in data during the interval. For realtime data, the value is the current minimum or current maximum. For historical data, the value is the average minimum or average maximum. For example, the following information for the CPU usage chart shows that the average is collected at statistics level 1 and the minimum and maximum values are collected at statistics level 4.
Summation – Data collected is summed. The measurement displayed in the chart represents the sum of data collected during the interval.
Latest – Data collected during the interval is a set value. The value displayed in the performance charts represents the current value.

Collection level 
Number of data counters used to collect statistics. Collection levels range from 1 to 4, with 4 having the most counters. 