readynas ultra6 fan speed

Is this NAS new to you or newly upgraded to OS6?  Do you know the fan and temperature reporting were working properly under OS 4.2.x?

I have now retired all my desktop units, but I did run an Ultra6 with OS6 and had no such problem. But I never got to OS 6.10.x, so maybe somebody who has an Ultra6 actively running that can let you know if the problem is common and maybe related to an update.

Looking at your system and CPU temperatures, one seems wrong.  Either the CPU temp is lower than actual, or the system temp is higher.  And my experience is that the ReadyNAS fan control really only looks at the CPU temp, and it's going to see yours as fine.  Does the temperature of the air coming out seem right for that reported system temperature?  If you turn it off and let it cool to room temp, do the temperatures look reasonable at the beginning?

If you're comfortable with SSH, can you check the response to cat /etc/sensors.d/system.conf?  Maybe something is just messed up with what the system is monitoring.  It should look like this:

chip "coretemp-isa-0000"
        label temp2 "CPU"
        compute temp2 @%35, @%35
        ignore temp3

chip "it8721-isa-*"
        ignore in0
        label in0 "V+12"
        compute in0 @*4, @/4
        set in0_min 10.8
        set in0_max 13.2
        label in1 "V5_0"
        compute in1 @*1.68, @/1.68
        set in1_min 4.7
        set in1_max 5.3
        label in2 "V3_3"
        compute in2 @*1.649, @/1.649
        set in2_min 3.135
        set in2_max 3.465
        ignore in3
        label in4 "V1_2"
        set in4_min 1
        set in4_max 1.3
        ignore in4
        label in5 "V1_8"
        set in5_min 1.5
        set in5_max 2.1
        label in6 "V-12"
        compute in6 @*19-50.4, (@+50.4)/19
        set in6_min -13.2
        set in6_max -10.8
        set in7_min 3.135
        set in7_max 3.465
        ignore fan1
        ignore fan2
        label fan3 "System"
        set fan3_min 400
        ignore temp1
        label temp2 "System"
        set temp2_min 1
        set temp2_max 80
        ignore temp3
        ignore intrusion0