How power measurements are processed in ITA
Power measurements can come from two sources:
- Data Center Expert
- The ETL import database. This includes importing manual measurements by uploading an Excel sheet.
The measurements tracked in DCO are:
- Peak power
- Average power
- Peak amps
- Predicted power, calculated based on the historical peak power measurements
The most interesting value for managing the data center is the peak power measurement observed within the last 30 days (configurable). This is the value typically shown in the user interface.
Predicted power is also actively used throughout DCO as estimated load. You can set this under Power Capacity; set Estimated Load Strategy to Predicted Power. When this strategy is used, power measurements are prioritized in capacity planning calculations.
The flow of power measurements is designed around the integration with Data Center Expert. The ETL integration tries to mimic the same behavior.
Polling for measurements
After DCO polls DCE for peak power measurements every 5 minutes (configurable), two things can happen:
- If it has been less than 24 hours since a full update of the power measurements was done, only the peak measurements are updated.
- If it has been more than 24 hours since a full update of the power measurements was done, there is a full update (peak and average for the last 24 hours).
Peak update of power measurements
DCO maintains values for the highest peak measurement observed over the last 30 days, configurable for the integration with DCE.
During a peak update, this value is updated if a larger peak measurement was found, that is, recent measurements affect the peak value.
If a larger peak value was found, the predicted power values are recalculated.
Full update of power measurements
Measurements during the last 24 hours are polled, then peak and average measurements are stored as historical values in the database.
If there are no measurements for devices, and there are already historical measurements, the historical value is copied and reused it as the measurement for the last 24 hours.
The highest observed peak values for both amps and power are recalculated.
A job is started that recalculates the predicted power values.
There is a special case when there have been no measurements for several days. This typically happens right after you set up DCO, or when the server was stopped for multiple days. DCO performs a catch-up process to get measurements from as far back as 30 days (not configurable).
Catch-up means that DCO looks at the latest measurement, up to 30 days back, and the time this measurement was taken. Then the measurements for 24 hours immediately after that are polled. If no measurement is found, the existing measurement is duplicated with a new timestamp. This process is repeated when there is less than 24 hours between the current time and the last measurement time.
There are no historical measurements because the DCO server was just installed and started: 30 day catch-up is performed
The server was shutdown for 10 days: 10 day catch-up is performed
When are measurements reset?
The 30 days that the peak calculations look back is configurable for the DCE integration.
Sometimes, when making changes to the database, the historical peak values are no longer interesting. There are two cases where DCO marks measurements older than some timestamp as invalid.
- When equipment is removed from a rack
When you remove equipment from a rack, the historical measurements are no longer valid. DCO saves a timestamp for the most recent time when equipment was deleted from a rack, and does not look further back than this timestamp for the measurements it uses. Just after a delete, no measurement is available, so DCO shows the previous measurement until a new one is available. When the measurements comes from an integration with DCE, this typically happens within a few minutes.
If no measurement is available within the next 24 hours, the previous measurement will be used for that day, even if it was taken before the timestamp, since no other measurement is available. This is important to note when importing manual measurements through Excel, or when using the ETL database in a non-automated way.
- When the assigned customer changes
The process described above happens for relevant equipment when you update the customer assigned to a rack or cage.
Another thing to note is when equipment is planned to be added using work orders (requires the Change module), DCO tries to include the equipment in the capacity calculations. Since the equipment is not installed yet, it has not yet affected the measurement; when using the predicted power capacity strategy, the adjusted nameplate of planned equipment is added to the estimated load.
What happens when the highest observed peak was 30 days ago?
Since the user interface shows the highest peak over the last 30 days, it is interesting to understand what happens when the highest peak measurement becomes older that 30 days. In the typical setup with DCE, there are unique measurements for each day; when the previously highest peak becomes 31 days old, the new highest peak from the last 30 days is shown.
How does this work with manual breaker panel measurements?
This is, in principle, the same thing that happens when you have manual breaker panel measurements uploaded in an Excel sheet. However, with manual measurements, a new measurement is typically not made every day. This means the previous measurement is duplicated for each day you do not have a measurement.
If you observe and import a measurement of 10 amps on day 1, and import an updated measurement of 5 amps on day 15, the measurement from day 1 is duplicated for each day from 2 to 14. Only after 30 days, on day 45, will the 10 amps measurement leave the history and the value in DCO change to 5 amps.