The curious case of the CPU rise in temperature, a rapid rise:
These statistics are from LibreNMS. Panic sets in, because this is a super NB server. The rapid rise starts on Wednesday at 3PM and at 2 AM alerts are sent out. Note the dip in the graph Thursday around 8AM. This is the data centre investigating:
No anomalies found at all but to help isolate a drop in organized in the aisle.
A more thorough investigation find that the hypervisor’s CPU cycles have increased at exactly the same time as the temperature problem. Additionally, other hypervisors had no increases in temperature.
Investigation leads to this really good Dell knowledgebase article.
You want to understand Maximum Performance Profile and Fan Speed Offset
Max Performance Profile
System Thermal Profile Optimization can be modified to Maximum Performance (Performance Optimized). This thermal profile carries the following advantages:
- Reduced probability of memory or CPU throttling.
- Increased probability of turbo mode activation.
- Generally, higher fan speeds at idle and stress loads.
Thermal Profile Optimization can be modified through following methods:
iDRAC9 GUI >> Configuration >> System Settings >> Hardware Settings >> Cooling Configuration
Fan Speed Offset
Fan speed offset allows you to increase the system fan speed with four incremental steps. These steps are equally divided between the typical baseline speed and the maximum speed of the server system fans. A fan speed offset causes fan speeds to increase (by the offset % value) over baseline fan speeds calculated by the Thermal Control algorithm. Possible values are:
- Low Fan Speed — Drives fan speeds to a moderate fan speed.
- Medium Fan Speed — Drives fan speeds close to medium.
- High Fan Speed — Drives fan speeds close to full speed.
- Max Fan Speed — Drives fan speeds to full speed.
- Off — Fan speed offset is set to off. This is the default value. When set to off, the percentage does not display. The default fan speed is applied with no offset. Conversely, the maximum setting will result in all fans running at maximum speed.
Fan Speed Offset can be modified through following methods:
iDRAC9 GUI >> Configuration >> System Settings >> Hardware Settings >> Cooling Configuration
Here is a screenshot:
The powerful effects of thermal management using iDRAC is immediately felt:
Real number of that screen is incredible! From 19 degrees inlet and 43 exhaust to 18 and 28!
Real cores down from almost 70 degrees to less than 40!
