UCS 5108 Chassis N+1 and GRID and PDU Cabling

[cowboycraig73]

I think this article is correct, would like to confirm.

Cisco UCS 5108 Chassis Power Policy Options and Redundancy Demystify
https://icookservers.blog/2018/04/05/cisco-ucs-5108-chassis-power-policy-options-and-redundancy-demystify/

The article has a gist of:
N+1 is for a PSU failure.
GRID is for a PDU failure.

Are the PSU ON/OFF modes below correct? 
GRID seems to be the way to go for 2 or 4 PDU's. 

PDU Cabling would be like this:
PDU-A = PSU1
PDU-A = PSU2
PDU-B = PSU3
PDU-B = PSU4

GRID Mode with (Option 1)
PSU1/PSU2 to A
PSU3/PSU4 to B

If a PDU fails - You are saved!

PSU1 – A ON
PSU2 – A OFF (Power Saving Mode)
PSU3 – B ON
PSU4 – B OFF (Power Saving Mode)

Thanks in advance for any enlightenment on 5108 Chassis Power.

[sgaree · Accepted solution]

This is correct, except for that last bit on Power Saving Mode.  You can't have a PSU turned off, because if a Grid goes down you'll be left with only one PSU, unlikely to support the load.  A PSU cannot be turned on out of power saving fast enough to support redundancy.  Power Saving is ignored when N+N is selected.

[cowboycraig73]

Thanks Very Much!