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DC power storage arrays are also more expensive than AC versions. "You're paying the premium for the more expensive power supply, but it's not dramatic," says EMC's Krone. McClure says Dot Hill's 5730 array, which can scale to 108TB of capacity, lists for $32,000. The price for the DC version would be approximately $500 more per power supply, with two power supplies in each 5730.
But with electrical power beginning to be priced on cycles, "if you went to DC power and had a DC backup system that provided four hours of backup, you could go two to three hours on your batteries and not have to buy peak price electricity," notes McClure.
There are other DC variations on the market. Validus DC Systems, a six-year-old company in Brookfield, CT, offers a hybrid AC-DC power system it claims can cut energy consumption by as much as 40% by eliminating AC power inside the data center, and running server and storage supplies at a higher DC voltage.
Validus CEO Rudy Kraus believes AC power has no place in the data center, just as it has never had a place in telcos. AC power allows electricity to be transmitted over long distances and at high voltages in relatively inexpensive wires, says Kraus. And considering that all the equipment in a data center runs at 12 volts DC, it doesn't make much sense to bring AC inside the data center, step it down a bunch of times, and then convert it into DC
| power inside the power supply for a server or storage array, he says.
However, "long legacy standards are hard to displace, so I think the uptake on DC power will be slow and deliberate," says Dave Reinsel, group VP, storage and semiconductor research at IDC (and co-author of the worldwide power and cooling study noted earlier). "Other power conservation strategies will likely be adopted first, such as increasing data center temperatures, data center HVAC design and tweaks, storage efficiency like dedupe and optimized disk drives."
This was first published in September 2008