For nearline applications like backup and archiving, any old SATA disk drive won't do, say vendors; you want a drive that has been tested using workloads that approximate the actual environments it will be used in.

Seagate's NL35 drive, in qualifications with interested channels, "fits the standard definition of SATA in terms of performance, but it's rated in a nearline workload," says Pete Steege, Seagate's senior product manager for enterprise storage. That means that unlike desktop drives, which are frequently powered up and down, the NL35 is rated to a continuous 1 million hour meantime before failure (MTBF) rate.

Another NL35 feature is workload management, which monitors the drive, throttles it if it's being overused and issues read-after-write commands. That reduces wear on the head, Steege says, and "ensures that what you wrote is really there." Improved error-recovery control, meanwhile, prevents drives from being taken out of commission prematurely. SATA drives can sometimes heal common errors on their own, but applications used to more reliable SCSI and Fibre Channel drives will time out waiting for a response and "assume that the drive must be dead," Steege explains. In fact, "the drives are fine." Better error recovery "tells the system 'I have a problem and I am working on it,'" he notes.

All these features sound well and good, but they come at a price, albeit a small one. Steege estimates the NL35 will be priced approximately 10% higher than a comparable desktop-class SATA device.

Seagate is the first drive manufacturer to announce a nearline-specific SATA drive, but it won't be the last. Mike Chenery, VP of advanced product engineering at Fujitsu Computer Products of America, says "[Seagate's] NL35 is a natural evolution in the industry." Fujitsu is also looking at ways to deliver SATA drives with lower annualized failure rates