PowerEdge dual power supply and power load balancing


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PowerEdge dual power supply and power load balancing

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We have a few PowerEdge 1950 and R710 servers with dual power supplies (PSU).

We have two completely separate power circuits (PDU) at our datacenter.

For each server we have connected a power supply to the first circuit and another power supply to the second circuit to obtain full power redundancy.

Will each server balance the power load across its two power supplies and thus the two datacenter circuits (e.g. active-active setup) or will a single power supply draw most of the power from a single circuit at any time (e.g. active-passive setup)?

I think what happens is the former, with load (almost) balanced between the two, but I'd like to get a confirmation from someone who actually knows that for sure or tested the setup.

Also, to get full redundancy, I think we need to keep the total power consumption low enough so that a single circuit can provide enough power to match the sum of the power currently drawn from both circuits, is that right?


All Replies
  • those systems dont load balance the power, one is strictly backup, it may draw minimal watts as a kind of keep alive, but definitely not load balancing system.

  • Actually according to this post it looks like the power supplies do load balancing:


    I just checked the power monitoring section in the DRAC web interface for a PowerEdge R710 and it shows a reading of 1.0A for each of the two power supplies.

    What do you think?


  • As to the two separate circuits.....

    Make sure each breaker in the electric box is on a different power phase leg. If you ever have power outages due to the electric company, the utility will likely try desperately to keep one of the phase legs powered, this how I have server rooms setup. In NYC's last blackout, Con Ed keep one of the phase legs powered, so none of my clients went down. Ask your electrician to check this for you.

  • yep, I was totally wrong on this one. I pinged a friend and was told: 
    The power supplies will split the load. But if the load is too light then one may take it all. Now if you remove one the other can take all the load whether or not the system is fully loaded.

  • Same subject related question...

    My understanding is that with Dual PSU servers both PSU's draw half the load required and share the internal supply to the server devices.

    However, during start-up is this still the case OR does the server draw from one PSU during the start-up phase and only draw on both PSU's when started?

    I think the first part of that is correct where both PSU's always share the internal load of the server BUT I'm constantly being told that during start-up just one is used, this seems illogical to me and I'm sure its wrong but....

    Anyone throw any light on this?