Performance Counter Data Collection

vSphere defines four levels of data collection for performance counters. Each performance counter specifies a level for collection. The historical performance intervals (PerformanceManger.historicalInterval) define the sampling period and length for a particular collection level.

The amount of data collected for a performance counter depends on the performance interval and on the type of entity for which the counter is defined. For example, a datastore counter such as datastoreIops (the aggregate number of IO operations on the datastore) will generate a data set that corresponds to the number of datastores on a host. If a vCenter Server manages a large number of hosts with a large number of datastores, the Server will collect a large amount of data.

There are other counters for which the vCenter Server collects a relatively smaller amount of data. For example, memory counters are collected as a single counter per virtual machine and a single counter per host.