HP BladeSystem Power Options – How to choose?

If you haven’t purchased the HP BladeSystem before, the power options may be a bit confusing. In particular, if you want to buy the large C-7000 chassis, and want to minimize the number of outlets you have a variety of options.

Each C-7000 chassis when fully populated with power supplies needs SIX power inputs, which would typically mean SIX outlets. Six?!? Yes, it’s power hungry. But to help reduce the cable mess and expense of installing six high current outlets, you can purchase one or more PDUs. PDUs (power distribution unit, AKA a honking big power strip) are also great for racks which may have two or three C-7000 chassis in them so you don’t need 12 or 18 outlets.

What are your options? First, I’d plan for the worst case which is two or three C-7000 chassis in a single rack. To know approximately how much power each chassis will require, use the HP BladeSystem power sizer. Second, check out the available PDUs from HP’s web site. For their honking large PDUs, see this link. For the BladeSystem, you only need the ‘core’ PDUs since the chassis plugs directly into the core PDU devices.

For redundancy, you should double the number of PDUs that you need to support your given rack load. You can then connect three power inputs from one PDU (or two depending on your load and PDU selected), and three inputs from another PDU (or two).

Each of the HP PDUs has a kVA rating. Consult the results of the HP BladeSystem sizer tool for the total kVAs that you need. Now that you know the number of kVAs you need, you should contact your facilities person and ask them what kind of power is available. Single phase? High voltage? Three phase? How many amps per circuit? Does your facility have dual power feeds or dual UPSes? Their input will likely determine what module you need to purchase.

For redundant PDUs, here are some quick rules of thumb:

— Two 24A three-phase PDUs can support one chassis
— Two 40A three-phase PDUs can support two chassis
— Two 60A three-phase PDUs can support three chassis

One critical fact you should be aware of, is that the three-phase PDUs have single phase outputs. So when you purchase your chassis, order the single phase C-7000 power option to go with your three phase PDUs. I’d stay away from three-phase chassis, as it’s better to go with three-phase PDUs and use a single-phase chassis power module to minimize the number of wall outlets.

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