If an IT shop chose data storage media strictly on the basis of energy efficiency, tape would be the clear winner. It sits on a shelf in a room, doesn't require power and needs little cooling. But with tape falling out of favor in data centers, one way to lower data center power consumption is to use energy-efficient disks such as SAS and SATA, as well as solid-state storage and tier storage so that the power-hogging disks are reserved for only those applications that truly need them.
Disks consume energy to varying degrees based on a number of factors. For instance, 2.5-inch disks use less power than 3.5-inch disks, 10,000 rpm disks require less energy than 15,000 rpm disks, and SAS disks utilize less power than Fibre Channel (FC).
"The most energy-efficient disk is the one that's not spinning, so classify data, get stale data off tier 1, increase utilization using good management practices," advised David Vellante, co-founder of The Wikibon Project, in an email.
With no spinning disks to power, energy-saving solid-state storage is increasingly becoming an option for tier 0, with the most I/O-intensive applications, although the cost premium in comparison with disk prices tends to leave many IT shops gun-shy at the moment.
But solid-state storage can potentially be cost-effective for IT shops that were compelled to bring in large amounts of high-performance hard disk drives (HDDs) or short-stroke disks to squeeze out better performance with especially heavy I/O-intensive workloads.
"For data that you need the fastest access to, where time is money, you're going to use the fastest drives that you can," said Teresa Worth, a senior product manager in enterprise storage at Seagate Technology LLC. "But how much of your data is really that super hot? Not that much -- maybe 10%, 20% at the most."
Worth said a tier of solid-state storage might make sense for select applications in certain IT shops. Solid-state technology fares much better with random reads and writes over hard disk drives, which have an advantage with sequential reads and writes, she added.
At present, IT shops with the highest performance needs have tended to favor 15,000 rpm Fibre Channel disk. But Fibre Channel has reached its final iteration (at 4 Gbps) as a disk interface, and market research firms such as Gartner Inc. and IDC predict Fibre Channel disk will disappear in the next three or four years, leaving only SAS and SATA disks.
That would be a shift in a positive direction from an energy-efficiency standpoint. SAS consumes less energy than Fibre Channel, and SATA requires less power than SAS. High-capacity, low-power SATA disks are the most environmentally friendly of the bunch, as well as the least expensive.
"A few years ago, it would have been unheard of to deploy, for example, Exchange [Server] on SATA drives," said Brian Garrett, vice president of the Enterprise Strategy Group Lab in Milford, Mass. "But now with vendors like [Dell Inc.'s] EqualLogic and [Hewlett-Packard Co.'s] LeftHand and all the mainstream vendors supporting SATA and proving that business use cases where you need mostly random access for online interactive users, instead of having a few really fast Fibre Channel drives, if you have enough SATA drives to meet your performance needs, you may be able to get away with lower energy-consuming drives."
Implementing a tiered storage strategy with a combination of SATA and SAS drives and solid-state storage can help to save energy as well as money. Automated storage tiering technology can ease the process. EMC Corp. claims its Fully Automated Storage Tiering (FAST) can lower system costs by 20% and operating costs, including energy consumption, by as much as 43%.
"Being able to optimize not only the storage infrastructure but the workloads to the storage tier that's required for its performance level could definitely help in driving down power and cooling costs," said Bob Laliberte, a senior analyst at Enterprise Strategy Group.