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In addition, some RAID controllers do preemptive rebuilds as a way of preventing disk failure. Controllers monitor the drives and then take a drive out of operation if there are signs of abnormal operation. This feature is far from ubiquitous, and not all RAID controllers perform this function the same way. According to StorageIO Group's Schulz, some vendors' firmware is overly sensitive, which can trip off false rebuilds; this can have a negative impact on performance due to the processing demands of the rebuild. "You really have to talk to other users and research the reputation of different systems," says Schulz.
Power consumption is a concern with drives of any size. The so-called "green storage" movement, which many vendors are scrambling to associate themselves with, promises products that expend less energy, generate less heat and generally make everyone feel good. For example, Seagate Technology offers a 1TB drive with PowerTrim, a feature it claims reduces power consumption at the drive level.
"If you're not using something, why power it?" says Whittington. "If you're doing a write, can you shut down all the read electronics and circuitry associated with that?" Depending on the app, in theory, this could translate into a significant reduction in power consumption.
Hitachi Data Systems and Western Digital also offer 1TB drives that accomplish power reduction using a variety of techniques, including idling the disks. These features could potentially increase reliability by reducing the amount of heat the drives are subjected to.
In a related note, drives that use solid-state memory as large onboard cache could emerge down the road. This additional memory would allow the drives to perform many operations while the disks sit idle, further reducing power consumption. [Note: Check out "Solid-state storage finds its niche"]
"Anything that involves flash, that makes sense; we'll be driving it for sure," says Whittington. However, according to Jerome M. Wendt, lead analyst and president at DCIG, this technology is most likely a long way off for most users.
--Andrew Burton
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