Cisco 9400 Power - Combined Mode question

[Chheang Va]

Hello, can someone assist in clarifying a few things for me.

I have a Cisco 9407 with dual sups and 5 POE line cards. The switch is powered by 3 PSU (3200W) and it set to the default combined mode. According to my power output, only 2084W is being used out of the 9600W available (see output below). I understand that the combined mode will use all 3 PSU and share the load. However I'm not exactly sure what happens when 1 or 2 PSU fails. What I'm missing is the following:

1. What happens when 2 out of the 3 fails? According to the output, I should have enough power left to run off of 1 PSU

2. What about this statement? " Combined mode does not provide power supply redundancy. In combined mode, if one of the power supplies fails, the system will power down modules until the system power allocation is under the power budget of the remaining power supply" - Assuming I have enough power from the 1 PSU left, then no modules should power down correct?

3. Is it better to run in redundant mode instead of combine mode?

Thanks for the help.

MDF_FL2_SW1#show power detail

Power                                                       Fan States

Supply  Model No              Type  Capacity  Status        1     2     3     4

------  --------------------  ----  --------  ------------  -----------------------

PS1     C9400-PWR-3200AC      ac    3200 W    active        good  good  good  good

PS2     C9400-PWR-3200AC      ac    3200 W    active        good  good  good  good

PS3     C9400-PWR-3200AC      ac    3200 W    active        good  good  good  good

PS Current Configuration Mode : Combined

PS Current Operating State    : Combined

Power supplies currently active    : 3

Power supplies currently available : 3

Power Summary          Maximum

 (in Watts)    Used    Available

-------------  ------  ---------

System Power   1720    1720    

Inline Power   364     7880    

-------------  ------  ---------

Total          2084    9600  

[Reza Sharifi]

Hi,

Assuming I have enough power from the 1 PSU left, then no modules should power down correct?

That is correct. As long as one PSU has enough wattage to run the whole system, you should be fine.

Is it better to run in redundant mode instead of combine mode?

On the 9400 combine is default mode. So, with combine, you are using all the PSUs but with redundant you are using one of them and until the one one fails than you use the another one. In redundant mode, each power supply needs to have enough power to run the whole system by itself but in combine that is not the case. I personally prefer the combine mode.

HTH

[Chheang Va]

Reza,

Thanks for the clarification.