Published: 11 Aug 2008
| Massive array of idle disks (MAID) has become synonymous with disk spin-down, which has become synonymous with power savings. That's not the way MAID pioneer Copan Systems saw it when it rolled out the first MAID system in 2004. Power savings were merely one benefit, along with increasing the life of low-cost SATA drives by using them less and lowering the cost of disk-based backup and archiving.
As green computing has gained in popularity, vendors that followed Copan into the disk spin-down space have made it more about power savings. Hitachi Data Systems calls its spin-down technology Power Savings Storage Service, and offers it for Fibre Channel (FC) as well as SATA drives in its midrange storage arrays. Nexsan Technologies recently made its AutoMAID available on SAS drives.
And more is coming: EMC released its first spin-down product this year with plans to offer the technology on all of its disk products, and ONStor is planning to add MAID on its Pantera NAS boxes this year.
With other vendors now crowding its turf, Copan's new mantra is: There's more to MAID than disk spin-down.
"MAID wasn't developed only to save power; it was to add other functions to disk drives," says Chris Santilli, Copan's CTO. "First, we can put more disk drives into a single cabinet than other systems in the industry. And we add reliability and/or disk service life. If disk drives aren't on all the time, the MTBF [mean time between failure] will increase and you can have a longer drive life."
Santilli claims that drives in Copan's Revolution systems have an average MTBF that's five to six times as great as the average disk drive. He says Copan will support SAS drives soon, and the company recently added features to reduce the performance penalty of MAID, such as setting up a cache landing zone that keeps up to 40 drives separate from the MAID pool so those drives always spin and increase the ingestion rate while handling data dedupe.
Mark Peters, an analyst at Milford, MA-based Enterprise Strategy Group (ESG), backs Copan's claim that MAID is more than just spin-down. "Copan came out with an implementation of MAID, and now everyone else is doing spin-down, which isn't strictly MAID," he says. "With a MAID system, you couldn't run all the drives even if you wanted to. More and more people are putting a spin-down capability into drives, but you could run all the drives if you wanted to."
But with power costs soaring--Framingham, MA-based research firm IDC estimates data centers spent $1 billion powering and cooling drives in 2007--it's no wonder MAID is catching on for its green powers.
| "It's strictly for power savings," says Chris Brown, VP of IT at Glenwood Springs, CO-based Alpine Bank, of his MAID implementation. "The slower you turn the drive, the less power you use."
Alpine Bank installed a Nexsan Assureon system with AutoMAID in mid-2007. Brown says he takes advantage of the different levels of AutoMAID. Level 1 retracts the hard drive read/write heads and responds to a request from data in less than a second. Level 2 slows the drive from 7,200 rpm to 4,000 rpm and spins back to full speed in less than 15 seconds at the first data request. Level 3 puts the drive in light sleep without turning it off, and can take 30 seconds to respond to a request. Nexsan claims power savings range from up to 20% for Level 1 to 60% for Level 3.
Alpine Bank uses Level 1 MAID for data that hasn't been accessed for five minutes and Level 2 for data that hasn't been accessed for 60 minutes. It doesn't use Level 3, says Brown, because "we're a 24 by 7 shop, so it probably wouldn't do much good. They'd be starting and stopping all the time."
Narayan Venkat, ONStor's VP of marketing, predicts the green craze will prompt all storage vendors to employ some type of MAID within a few years. "You have massive amounts of unstructured data on storage systems infrequently accessed," he says. "Why let it run overnight when nobody's accessing it?"
Of course, spinning down disks isn't the only way to save power in the data center. In June, Dot Hill Systems began shipping its 5730 FC system with a DC power option that lets companies save money by using DC power rather than the typical AC power.
ESG's Peters suggests a more low-tech way to decrease power usage by reducing the information stored on external disk. "Everybody gets excited about dedupe, but there's a thing called delete," he said. "More people should do more of that."