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Another option is to move data offline. Tape not only costs less than disk but uses less energy and requires less cooling. In her analysis of SATA disk and LTO tape, "the cost to acquire, power and cool a disk system is almost eight times that of a tape library," says Dianne McAdam, director of enterprise information assurance at The Clipper Group Inc., Wellesley, MA. Of course, this means giving up the performance of disk.
Online archiving storage system vendors, like Copan Systems Inc., offer disk systems that shut down the spindles when the data on them isn't accessed frequently. Copan has recently begun touting its energy efficiency, claiming to be five times more energy efficient per terabyte than conventional storage.
"Copan could deliver interesting energy savings," says McAdam. However, "whenever you power down disks, there are potential problems bringing back individual drives," she warns. Some data may not come back. Copan automatically powers up each idle drive at least once a month to check for data errors and rebuilds the drive if necessary.
At his Midwest financial organization, Thomas uses some Copan arrays--but not because of any promised energy savings. "We use Copan in our biggest data centers to replace tape because of floor space issues," he says. The smaller Copan footprint was quite attractive. "When we look at all of our data center costs, real estate is still a bigger headache than power," notes Thomas.
After boosting utilization, rearranging the data center and moving data offline, storage managers are left with replacing storage devices with more efficient devices. Healthy Directions LLC, a large newsletter publisher in Potomac, MD, reduced its power consumption by 50% over the last few years by replacing old servers and consolidating DAS storage onto a 10TB StoneFly Inc. iSCSI SAN, says Edward Brookhouse, principal engineer, network operations. However, he fears energy consumption will go up as the organization migrates to densely packed blade servers.
This was first published in March 2007