Reasons to go Green
As you can see in the table on the previous page, the newer Samsung HD103SI draws about three watts less power than the older HD321KJ. While this is partly due to the slower rotation speed of its 5,400 RPM spindle, other technological advances in hard drive manufacturing also contribute to the lower power consumption.
When a computer or NAS is equipped with a single hard drive, a power consumption difference of only three watts is negligible. However, that should be the exception for NAS devices. Loaded with the four drives our testbed system can house, the difference jumps into the two-figure range. And that can definitely make a difference when the time comes to pay your electric bill. A welcome side effect is that the NAS stays cooler as well, which also means that the unit runs quieter since its fans can spin more slowly.
Those worried about having to pay a premium for a more eco-friendly hard drive model can relax, as disks with a spindle speed of “only” 5,400 RPM tend to be slightly less expensive than faster drives aimed at the performance segment.
Does Eco mean Lower Performance?
But what about performance? Is there a penalty for using an eco-friendly drive in a NAS device? As mentioned above, when we take a look at the components that make up a typical NAS, we find that the hard drives are not actually the bottleneck. Rather, it’s often the NAS’ RAID engine.
To keep their appliance's prices at an affordable level, manufacturers often forego the inclusion of a dedicated processor for this task, instead letting the NAS’ host processor handle the burden of XOR calculations required for RAID levels 5 and 6. On the downside, this method is much less efficient than having a dedicated RAID chip. As a result, data throughput is highly dependent on the processor that a NAS uses.