One of the servers I currently mange is a Dell PowerEdge R750 that came pre-installed with iDRAC firmware version 5 (5.10.50.15). During planned maintenance, I upgraded to the latest iDRAC firmware version 6 (6.00.02.00). Immediately after installing, I noticed the fans were running much louder than before.
Checking within iDRAC under System > Cooling, the fans were running at 29% PWM, even though the ‘Thermal Profile Optimization’ was set to ‘Default Thermal Profile Settings (Minimum Power)’ with a ‘Minimin Fan Speed’ set to ‘5% PWM’.
Within ‘Configure Cooling’ (or Configuration > System Settings > Hardware Settings > Cooling Configuration), you have the following settings:
Automatic Fan Speed Calculation
Thermal Profile Optimization: Default Thermal Profile Settings
Fan Speed Offset
Fan Speed Offset: Off
Thresholds
Minimum Fan Speed in PWM (% of Max): Default
Changing these settings made no difference to fan speed, with offset only increasing it further. It does not accept a negative offset value.
I therefore decided to rollback the iDRAC firmware back to version 5, and once finished, the fans returned to around 6% PWM.
To rule out this being a bug in the newly released version of iDRAC, I waited until another update was released and tested upgrading again. The same thing happened, and rolling back the firmware update retuned fan speeds back to their lower levels.
When iDRAC firmware version 7 was released, tried upgrading and the same thing happened. It appears there has been a change in later versions which is causing the fans to spin unnecessarily higher, even when the hardware remains the same.
The R750 is currently running the following configuration:
At the time of writing, using iDRAC version 5 firmware, the server is running under the following conditions:
I’ve just taken delivery of a Dell PowerEdge R760 with the following specification:
This unfortunately comes pre-installed with iDRAC firmware version 7, and will not let me downgrade to iDRAC firmware version 5.
The server is currently idle, no VMs running on it and is reporting the following values:
I’d submitted a ticket with Dell to find out if there was a way of reducing fan duty beyond where it sat, however, they said they can only fix or replace, explaining that it is up to the engineers who write software for iDRAC to address. There is no way to directly contact this department for advice or to suggest improvements, and unless this issue is identified at scale with multiple customers reporting it, nothing is going to get done about it.
The closest I got to an explanation was that the BOSS controller NVMe SSDs need to be kept cool, and with them being at the back of the server, the fans need to spin higher to accommodate this. However, in diagnostic reporting, these NVMe SSDs were also well under threshold temperatures, so I felt this didn’t explain which component in the server was preventing the fans from achieving a lower PWM.
Great! I suppose this means I’m now stuck with a server that is unnecessarily louder than it needs to be in a ‘noise sensitive’ environment (Dell’s words in iDRAC!). I get this is a 2U rackmount server, however Dell don’t sell anything in tower form that could utilise larger fans spinning at a lower speed whilst maintaining similar air flow.