Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

Power Consumption in UCS

Hi,

We are running 4 Chassis in our enviroment with firmware 1.4 (3q) and recently we had an issue with one of the PSU (PSU2) in chassis 2 and we got it replaced and after that we are observing that 1 of the PSU in each chassis is showing as "Power Save" (PSU-Details_All_Chassis.JPG) state.

I want to understand that how Power consumptions works in UCS, I have also attached "Power Groups" (Power-Group_Details.jpg) snap shot for the reference.

Want to understand what is "unbounded" & "cap-ok". When will "power save" state PSU will be ON state and does it will go again in "power save" state.

PSU-Details_All_Chassis.JPGPower-Group_Details.jpg

Thanks,

Amit Vyas

2 ACCEPTED SOLUTIONS

Accepted Solutions

Power Consumption in UCS

Amit, if the PDUs in the diagram are going to 2 different power sources then I would swap cords 2 and 3 and then configure the UCS power policy as grid. With grid PSUs 1, 2 are in one grid and PSUs in 3,4 are in the other grid.

With grid you could lose a PDU and the system would stay up. N+1 is recommended when all PSUs are going to a single power source.

Take a look at this for more detailed info on the PSU grids and options

http://www.cisco.com/en/US/docs/unified_computing/ucs/hw/chassis/install/overview.html#wp1255314

Cisco Employee

Power Consumption in UCS

Amit,

Again Jeremy is correct. given your illustration grid is the way to go.

The best way to figure out your power requirements however is to use the following tool:

http://www.cisco.com/assets/cdc_content_elements/flash/dataCenter/cisco_ucs_power_calculator/

To answer your question however about the N+1 I have included an explanation below.

Also instituting power capping at the chassis level requires the following:

    IOM, CIMC, and BIOS version 1.4 or higher

    2 PSUs

A minimum of 3788 AC watts should be set for each chassis. This  converts to 3400 watts of DC power, which is the minimum amount of power  required to power a fully-populated chassis.

This means that after 1.4 release the minimum with power capping is 2 PSUs. For example previous to 1.4 release a system that was set for N+1 (1+1 for example) would need to have 3 PSUs N+1 (2+1) in releas 1.4 and greater. This is because of the power groups minimum requirement.

If the power is required the +1 should be made available to meet the redundancy requirements. If it is not needed it is turned off / power save.

Please let me know if this helps.

10 REPLIES
Cisco Employee

Power Consumption in UCS

Amit,

Please have a look at the following document. I think it will answer your questions.

Managing Power in Cisco UCS

http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/gui/config/guide/1.4/UCSM_GUI_Configuration_Guide_1_4_chapter29.html

Unbounded—The server is not power capped under any circumstances.

Note       

Power capping only goes into effect if there is insufficient power available to the chassis to meet the demand. If there is sufficient power, the server can use as many watts as it requires.

New Member

Power Consumption in UCS

Anika,

Thanks for providing the link but still i wan to understand that why 1 PSU in each chassis showing as "power save" mode ? what will be the reason for this ?

Also want to understand when this "power save" state PSU will be utilize?

I hope you are any one from cisco will answer it.

Thanks,

Amit Vyas

Power Consumption in UCS

Amit, it is probably because your Power Policy is configured as n+1. In this mode UCS will keep 1 PSU in a standby state and will only bring it online if a PSU fails.

If you have 2 power sources for your chassis where 2 PSUs are going to 1 source and 1 to another then you want to configure the power policy as grid. With grid all 3 PSUs are used.

Take a look at this for more info

http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/gui/config/guide/2.0/b_UCSM_GUI_Configuration_Guide_2_0_chapter_0100000.html#d12962e127a1635

New Member

Power Consumption in UCS

Jeremy,

We are using N+1 power policy in our setup. I am attaching power cabling diagram for USC at enviroment. I want to understand in N+1 power policy... N=? how many number or whatever ?

In below scenario will you suggest me to configure "grid" power policy or current policy (n+1) is suffiece.

Thanks,

Amit Vyas

Power Consumption in UCS

Amit, if the PDUs in the diagram are going to 2 different power sources then I would swap cords 2 and 3 and then configure the UCS power policy as grid. With grid PSUs 1, 2 are in one grid and PSUs in 3,4 are in the other grid.

With grid you could lose a PDU and the system would stay up. N+1 is recommended when all PSUs are going to a single power source.

Take a look at this for more detailed info on the PSU grids and options

http://www.cisco.com/en/US/docs/unified_computing/ucs/hw/chassis/install/overview.html#wp1255314

New Member

Power Consumption in UCS

Thanks Jeremy for the link. I found it more explainer as I required.

Most of the doubts is been clear.

Thanks once again..

Regards,

Amit Vyas

Cisco Employee

Power Consumption in UCS

Amit,

     Jeremy is correct. I have included an excerpt from the documentation explaining the different modes.

  • non-redundant—All installed power  supplies are turned on and the load is evenly balanced. Only smaller  configurations (requiring less than 2500W) can be powered by a single  power supply.

  • n+1—The total number of power  supplies to satisfy non-redundancy, plus one additional power supply for  redundancy, are turned on and equally share the power load for the  chassis. If any additional power supplies are installed, Cisco UCS Manager sets them to a "turned-off" state.

  • 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.

Please let me know if this helps explain things better.

New Member

Power Consumption in UCS

Anikas,

Apologias to mention your wrong name in my previous post. Thanks for excerpt.

Correct me in below scenario.

My current utilization on Chassis-1 is average 1500W and I have configured N+1 power policy. According to the n+1 policy explanation the total number of power supplies to satisfy non-redundancy + one additional power supply for redundancy which will be like this 2 for satisfy non-redundancy and 1 for supply redundancy which will be 2+1 and one PSU is in power save state. Since my PSU is 2500W each and if i am using N+1 power policy so power will distributed in 3x2500W = 7500W. And if at all my chassis utilize more then 7500W power then PSU4 will be turned on?

I have attached power cabling diagram in replying to Jeremy's reply

Thanks,

Amit Vyas

Cisco Employee

Power Consumption in UCS

Amit,

Again Jeremy is correct. given your illustration grid is the way to go.

The best way to figure out your power requirements however is to use the following tool:

http://www.cisco.com/assets/cdc_content_elements/flash/dataCenter/cisco_ucs_power_calculator/

To answer your question however about the N+1 I have included an explanation below.

Also instituting power capping at the chassis level requires the following:

    IOM, CIMC, and BIOS version 1.4 or higher

    2 PSUs

A minimum of 3788 AC watts should be set for each chassis. This  converts to 3400 watts of DC power, which is the minimum amount of power  required to power a fully-populated chassis.

This means that after 1.4 release the minimum with power capping is 2 PSUs. For example previous to 1.4 release a system that was set for N+1 (1+1 for example) would need to have 3 PSUs N+1 (2+1) in releas 1.4 and greater. This is because of the power groups minimum requirement.

If the power is required the +1 should be made available to meet the redundancy requirements. If it is not needed it is turned off / power save.

Please let me know if this helps.

New Member

Power Consumption in UCS

Thank you Anikas for your inputs as well. Really appreciated.

Regards,

Amit Vyas

5440
Views
5
Helpful
10
Replies