Hybrid Hard Drives Are Not Ready for Data Centers
The recent release by hard disk maker Seagate of it’s Momentus XT Solid State Hybrid Drive—a disk drive that combines platter and flash memory storage in the same box—holds a lot of promise, but don’t expect to see its ilk in the data center any time soon.
The technology is expensive—the hybrid drives cost twice as much as standard hard disk drives with similar capacities—and contains wrinkles that make them less than plug and play for data centers. In a study of solid state storage in data centers, Microsoft concluded that the benefits of the technology simply can’t outweigh its detriments.
“We found that replacing disks by SSDs [Solid State Disks] is not a cost effective option for any of our workloads, due to the low capacity per dollar of SSDs,” the Cambridge, UK, researchers discovered. In their analysis, they reviewed workload traces from servers in both large and small data centers.
“Depending on the workload, the capacity per dollar of SSDs needs to increase by a factor of 3-3000 for an SSD-based solution to break even with a disk based solution,” the researchers maintained. “Thus, without a large increase in SSD capacity per dollar, only the smallest volumes, such as system boot volumes, can be cost-effectively migrated to SSDs.”
They added: “The benefit of using SSDs as an intermediate caching tier is also limited: fewer than 10 percent of our workloads can reduce provisioning costs by using an SSD tier at today’s capacity per dollar, and fewer than 20 percent can do so at any SSD capacity per dollar.”
A major plus for SSDs is energy savings. But those benefits are offset by the cost of the disks, the researchers noted. Moreover, they argued that comparable energy savings could be achieved with low-power SATA disks.
