DC VS. AC
There's no doubt that you'll benefit from reconsidering data center best practices. One practice that we don't recommend reconsidering is the use of DC systems rather than the AC systems that currently dominate the data center.

Certainly there's demand for DC power for any business that requires NEBS (network-equipment building system) compliance, primarily major telcos. Telcos have used DC for years, primarily for reliability and the ease with which alternative power sources (batteries and generators) can be brought online to supplement line power.

Also In This Report

>> Data center best practices

>> Full analysis of our 2006 poll with comparisons to 2005 research

>> A look at physical security issues

>> Guidance on designing for target availability

Get the full-length report at businessinnovation.cmp.com/
itopt

Other industries have considered DC power, and every major server vendor makes at least a few DC-powered systems. One that specializes in DC servers is Rackable Systems.

There are some major concerns that typically dissuade the use of DC. You'll have many fewer systems from which to choose. Engineering DC power throughout a data center requires specialized knowledge--one loose bolt on a DC bus system and you may end up melting the bus bar. You have to put the inverters on the roof to avoid their heat generation jacking up the data center's cooling requirements. DC systems tend to be more expensive than AC systems, so the overall purchase cost is higher (though DC systems do use less energy, so the total cost of ownership may still work out.) Finally, while there are DC servers, switches, routers, and storage devices, there aren't DC computer room air conditioners. That means you'll end up with both AC and DC in your data center, and it would obviously be better to have just one power system. For these reasons, DC data centers haven't caught on for general use.