Nexus 9396px switch FAN speed issue

[satish.txt1]

When i load nxos.7.0.3.I2.2d.bin Software then FAN running very quiet in following speed, Currently i am testing in LAB so i didn't plug two power supply.  

switch# sh environment fan detail
Fan:
---------------------------------------------------------------------------
Fan             Model                Hw     Direction       Status
---------------------------------------------------------------------------
Fan1(sys_fan1)  N9K-C9300-FAN2       --     front-to-back   Ok
Fan2(sys_fan2)  N9K-C9300-FAN2       --     front-to-back   Ok
Fan3(sys_fan3)  N9K-C9300-FAN2       --     front-to-back   Ok
Fan_in_PS1      --                   --     front-to-back   Ok
Fan_in_PS2      --                   --     front-to-back   None
Fan Zone Speed: Zone 1: 0x33
Fan Air Filter : NotSupported
Fan:
------------------------------------------------------------------
 Fan Tray            Fan   Fan Direction   Speed(%)  Speed(RPM)
------------------------------------------------------------------
Fan1(sys_fan1)      fan1    front-to-back    37        6136
Fan1(sys_fan1)      fan2    front-to-back    37        4895
Fan2(sys_fan2)      fan1    front-to-back    35        5825
Fan2(sys_fan2)      fan2    front-to-back    36        4753
Fan3(sys_fan3)      fan1    front-to-back    36        5973
Fan3(sys_fan3)      fan2    front-to-back    37        4838

But when i upgrade it with latest one nxos.7.0.3.I4.7.bin then it is running fast. Why? 

switch# sh environment fan detail
Fan:
---------------------------------------------------------------------------
Fan             Model                Hw     Direction       Status
---------------------------------------------------------------------------
Fan1(sys_fan1)  N9K-C9300-FAN2       --     front-to-back   Ok
Fan2(sys_fan2)  N9K-C9300-FAN2       --     front-to-back   Ok
Fan3(sys_fan3)  N9K-C9300-FAN2       --     front-to-back   Ok
Fan_in_PS1      --                   --     front-to-back   Ok
Fan_in_PS2      --                   --     front-to-back   Shutdown
Fan Zone Speed: Zone 1: 0x80
Fan Air Filter : NotSupported
Fan:
------------------------------------------------------------------
 Fan Tray            Fan   Fan Direction   Speed(%)  Speed(RPM)
------------------------------------------------------------------
Fan1(sys_fan1)      fan1    front-to-back    62        10325
Fan1(sys_fan1)      fan2    front-to-back    63        8256
Fan2(sys_fan2)      fan1    front-to-back    59        9872
Fan2(sys_fan2)      fan2    front-to-back    62        8071
Fan3(sys_fan3)      fan1    front-to-back    61        10169
Fan3(sys_fan3)      fan2    front-to-back    62        8071

I don't have TAC support on these switch so i can't open support ticket too but just curious if someone else having same issue. 

[Andrea Testino · Accepted solution]

Hi Satish,

Higher fan speeds may be seen for N9K/N3K TORs starting in code 7.0(3)I4(1) in later. These fan speeds have been changed to match HW recommended values. In other words, we changed the "minimum" speed that they can spin at after I4(x) thus you will continue to see this in upcoming releases and is expected behavior.

Nothing to worry about :)

Hope that helps!

- Andrea

[satish.txt1]

+1 You are awesome!!!  Andrea, 

Just curious does this thing covered or documented in software release? It would be good to see official announcement so people like me don't get panic.

Thank you for quick reply :) 

[Andrea Testino]

Satish,

Thank you! Glad to help. It would appear we've not documented this into our Release Notes for the I4(x) or later releases. I'll see if I can get that added to avoid panic as you mentioned!

Thank you for the feedback.

- Andrea

[bd-fisher]

Hi Andrea,

There is still no mention of this in the release notes. Can you possible send a link ???

We have four 9364c switches running 7.0(3)I7(2)

One was upgraded to 7.0(3)I7(6) and the fan speeds doubled.

Also noticed that the "show env fan detail" indicates a different model with the upgraded version:

All 3 other switches have a fan model = NXA-FAN-30CFM-F (would be odd to have one switch with different fans)

PGH-ROCK-9364-02# sho env fan det
Fan:
---------------------------------------------------------------------------
Fan             Model                Hw     Direction       Status
---------------------------------------------------------------------------
Fan1(sys_fan1)  NXA-FAN-160CFM-PE    --     back-to-front   Ok    
Fan2(sys_fan2)  NXA-FAN-160CFM-PE    --     back-to-front   Ok
Fan3(sys_fan3)  NXA-FAN-160CFM-PE    --     back-to-front   Ok
Fan_in_PS1      --                   --     back-to-front   Ok
Fan_in_PS2      --                   --     back-to-front   Ok
Fan Zone Speed: Zone 1: 0xc2
Fan Air Filter : NotSupported
Fan:
------------------------------------------------------------------
 Fan Name          Fan Num   Fan Direction   Speed(%)  Speed(RPM)
------------------------------------------------------------------
Fan1(sys_fan1)      fan1    back-to-front    74        8910
Fan1(sys_fan1)      fan2    back-to-front    76        8598
Fan2(sys_fan2)      fan1    back-to-front    74        8881
Fan2(sys_fan2)      fan2    back-to-front    76        8598
Fan3(sys_fan3)      fan1    back-to-front    73        8837
Fan3(sys_fan3)      fan2    back-to-front    76        8557

Is all of this normal for the upgrade?

Regards,

Brian

[Andrea Testino]

Brian,

Thank you for reaching out. I've followed up with our Documentation team about this. You should see mention of the fan speed change in our NX-OS Release Notes https://www.cisco.com/c/en/us/support/switches/nexus-9000-series-switches/products-release-notes-list.html starting at the 7.0(3)I7(3) Release Notes. It should take 24-48 hours more or less for the changes to be public.

Thank you!

[paulstejskal]

FYI it's noted there but about 3/4 of the way down: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/7-x/release/notes/70373_nxos_rn.html

Limitations

This section lists limitations related to Cisco NX-OS Release 7.0(3)I7(3).

■        When you upgrade a Cisco Nexus 9000 device to Cisco NX-OS Release 7.0(3)I7(3), if a QSFP port is configured with the manual breakout command and is using a QSA, the configuration of the interface Ethernet 1/50/1 is no longer supported and will need to be removed. To restore the configuration, you must manually configure the interface Ethernet 1/50 on the device.

■        Due to the design of airflow, back-to-front fans requires fan speed to be run at full speed all the time. You might also see fan speeds increase from 40% to 70% post-upgrade. This applies to the following PIDs: N9K-C9272Q, N9K-C9236C, N9K-C93180YC-FX, N9K-C93180TC-FX, N9K-C9364C, N9K-C9336C-FX2. This change is made as of cisco NX-OS Release 7.0(3)I7(3). If your PID is not listed, please contact Cisco TAC for additional verification.