vCenter Server collects statistics from the guest operating system at regular intervals and stores them in a database. Users can query the statistics in the database by selecting a time period and a roll-up function that vCenter Server applies to the statistics before returning them to the client.
After the monitoring service starts up, it begins requesting statistics from the guest operating system periodically, at a frequency that depends on the type of statistic. The service requests storage statistics once every 10 minutes, while it requests memory, CPU, and networking statistics once per minute. The collection times are fixed relative to the startup time of the monitoring service, rather than to clock time.
The monitoring service retains statistics approximately 13 months, by default. Older statistics are deleted by the service, creating a 13-month moving window within which you can query statistics. You can choose to delete statistics as needed to conserve storage resources.
