I have the same issue. Started over the past week. I have two power supplies in the MFSYS25. If I pull PS2, the fan noise is much quieter. If I install PS2, it's quiet for a few minutes, and then resumes it's high speed.
The Fan Tachs on the Intel Modular Server Dashboard show within range at around 5600rpm. Middle of range, actually.
I tried another spare PS in PS2 slot, same issue.
I'm running the latest 6.8 firmware form July 2011.
Similar issue. The temp in the server room was a little high (82 deg F, but it has always been around 80 deg in that room) so I put some cooling in place and got it down to 75 deg F. That made the following changes in measurements according to the management software (all in Celsius):
LOCATION 1st READING 2nd READING
Dashboard amb.temp 25 23
Drives 29-33 26-27
upper rear sys fan 29 27
lower rear sys fan 27 25
PSU#1 34 34
PSU#2 35 35
PSU#3 37 37
PSU slot 4 32 32
Chassis front IO fan 25 23
First steps were to take the servers down. I removed every removable component and vacuumed and/or used compressed air to clean out any fuzz. Upon restart the system was running normally - that is the fan speed were what I expected and have experienced for the three years this system has been in service.
Five days later the fan speed ramped up again. And as another poster said-these are the rear system fans that are tach'ing around 4200-4300 rpm--normally they run at 2400-2600 rom.
We are on firmware
This is the first generation chassis.
My confusion stems from the fact that this began spontaneously with no obvious cause. We are taking down the chassis tonight to try and get the fans to reset.