The Raritan Blog

Data Center Cabinet Load Balancing:  there’s a less complicated way.

Scott Fier
March 28, 2017

Why do we load balance?

Without going into the complicated math, suffice it to say that load balancing in a 3 phase system is desirable.  The more unbalanced a system the more problems it creates.  UPS life, for one, can be affected by unbalanced systems.  Although one circuit (server cabinet) being out of balance won’t have much effect, if many or all circuits on a panel are out of balance, the main circuit supplying the breaker panel will be out of balance and this can ruin your upstream UPS.  There are also efficiency issues with unbalanced loads.

How is load balancing currently accomplished in a rack cabinet?

To balance a load in a cabinet, the loads of the equipment power supplies are spread across the 3 phases – L1/L2, L2/L3, L3/L1.  This is done by plugging the first server (or switch/router) in an outlet wired on L1/L2, the next server on L2/L3, the next on L3/L1, then start over.  The goal is to get an equal number of devices/loads on all 3 phases – or as close as possible. 

This approach can quickly turn into a cabling nightmare. Most rack PDUs are linear in their phase layout of outlets – there are only three banks of outlets, one for each phase.  For example, on a 36 outlet PDU, outlets 1 through 12 will be on L1/L2, 13 through 24 on L2/L3, and 25 through 36 on L3/L1.  If you use the above method of balancing, and start racking the devices at the bottom U position, the third device you plug in will need to reach the top third of the PDU and the last device may have to reach back to the bottom of the PDU.  In other words, a lot of crisscrossed cabling.

How do Raritan’s balance the cable and load balancing challenge?

In certain Raritan PX three-phase models the architecture gets around the cabling issue by staggering the grouping of outlets - there are at least 6 banks of outlets.  For example, outlets 1 through 6 are on L1/L2, 7 through 12 on L2/L3, 13 through 18 on L3/L1, but then we start over at L1/L2 for outlets 19 through 24. (See Illustration below)

This intelligently engineered architecture results in more reliability and easier execution.  The devices towards the top of the cabinet don’t need to be plugged in to the bottom of the PDU and devices at the bottom don’t need to be plugged in to the top.

ASHRAE 90.4: A more sophisticated standard

Nicolas Sagnes
January 25, 2017

In September of 2016, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) published a new and improved standard that establishes the minimum energy efficiency requirements for data centers.

How LinkedIn Scaled Data Center Operations with Three-Phase Power

Liz
October 7, 2016

LinkedIn, Data Center Knowledge, and Raritan have joined forces to share unique insights on bringing three-phase power chains all the way to the rack.  The three companies will be participating in a webinar this month on “How LinkedIn Scaled Data Center Operations with Three-Phase Power.” 

PDU Mass Deployment and Lifecycle Management

Nicolas Sagnes
August 17, 2016

You recently acquired brand new PDUs or you are in the process of evaluating power distribution solutions. You are probably asking yourself: “How can I easily and seamlessly deploy my PDUs and leverage their capabilities in my existing DCIM software or BMS?”

Well, look no further. I’m here to give you a quick overview of Raritan’s open API and scripting capabilities, as well as our mass configuration options.

New Two Minute PX Rack PDU Video

Michael Bord
August 15, 2016

What sets the PX series of intelligent PDUs apart from other power strips? Greater value. And that goes beyond reliable power distribution. It's about improving uptime and capacity management.  Saving energy and reducing your carbon footprint.  Managing geographically dispersed infrastructure that needs to be more reliable than ever before.  In short, it's about meeting the challenges you face in your everyday life head-on, with solutions that are engineered with you in mind.  Watch this new clip to see exactly what we mean. 

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