5108 chassis and power failure

[MrTan]

Hello all,

I have a fully populated 5108 chassis with 8 x B200 M5 servers.
The chassis has 4 power supplies which are configured in a grid mode.
Power supply 1+2 are connected to the same PDU and power supply 3+4
are connected to a different PDU.

What will happen if I lose one of the PDU's, will the chassis be able to handle
all the 8 x B200 M5 servers at full power?

Thanks in advance,
Ron.

[balaji.bandi]

if you configured Grid Mode : ( as per my experience you are ok, if one of the PDU) - Hope you have 2 Different source of Power - Essential and non essential kind.

My Live environment running, when i do sat test before put them in to production it was ok, as of now, not seen any Power failures.

Grid – Two power sources are turned on, or the chassis requires greater than N+1 redundancy. If one source fails (which causes a loss of power to one or two power supplies), the surviving power supplies on the other power circuit continue to provide power to the chassis.

[MrTan]

Each PSU is capable of handling 2500W. 4 x 2500W = 10000W.
If 2 PSU's will fail (that means that one PDU is down), the chassis
will have half of its power which means 5000W.

I have calculated the amount of power required for the 8 x B200
servers on the Cisco UCS Power Calculator website
(https://ucspowercalc.cloudapps.cisco.com/public/index.jsp)
and got a result of 5250W.

5250W is more than 5000W. What will happen to the servers?

[ITM-Team]

You could check your current power usage via UCS Manager:

Select Chassis -> Power -> Statistics

There you can see the average, max and min usage summarized for the chassis and also separated for the servers.

I checked some of our chassis, e.g. a fully populated 5108-AC2 with 8 running B200 M5 servers consumes max 2464W.

I can remeber we did several outage tests some time ago and the chassis could handle the failure of 2 psus.