Just before you head over to your favourite online emporium, bear this in mind: Western Digital has refreshed its VelociRaptor lineup of spinning hard disks to include larger capacities, bigger caches and, crucially, reasonable prices.
Suddenly, the decision between traditional storage and SSD isn't quite as easy to make. The VelociRaptor range has been around for about a decade now and, until the advent of SSDs, was the storage of choice for the discerning gamer or those who needed workstation speeds for video editing and the like. Just like SSDs, the original VelociRaptors were fast, expensive and lower capacity than regular drives, best used for speeding up particular tasks rather than bulk storage.
With flash memory prices falling through the floor and traditional hard drive prices still high after last year's Thai floods, a betting system builder might have put money on the VelociRaptor fading away this year as a superseded technology. Western Digital, however, isn't prepared to let them go the way of their dinosaur forebears. And the combination of new features in the models makes them very clever lizards indeed.
The key thing that separates a VelociRaptor from an ordinary hard drive is spin speed. They are high rotation server drives packaged for desktop use. That means quicker seeking of information, along with faster read and write speeds. The downside to this is, of course, the exceptional level of engineering required to operate at such velocities, and the resulting cost - which has always been considerably higher than an equivalent 7,rpm drive.
However, there is one other benefit. Drives running at 10,rpm are - the VelociRaptor excluded - almost only used in demanding professional situations. So there's a five-year guarantee and a good reputation for reliability behind them too - a nice extra for those who worry about investing an SSD because of negative longevity claims. What's new in the latest version of the VelociRaptor?
While it's true that most client workloads don't require the sort of random IO performance a high-end SSD can provide, it's the additional headroom that SSDs offer that allow performance to remain high regardless of what's going on in the background. We can look at this data another way, instead of average data rate let's look at the maximum number of IO operations these drives can service in a single second:. Based on this list, the average hard drive excluding WD's 10, RPM drives is capable of handling around 4KB pseudo-random write operations per second.
Upping the spindle speed to 10, RPM gives you a bit of a reprieve, more than doubling performance, but that's not always sufficient given the workload. At the other end of the spectrum we have a stanard 3Gbps SSD, capable of servicing nearly 15, 4KB write operations per second.
No desktop application could be shipped that required this type of IO performance as it would be unusable on any hard drive. The added performance in the case of an SSD doesn't deliver 21x the performance of a VelociRaptor, but it offers enough performance headroom that applications and file accesses will remain as fast as possible regardless of what's going on in the background.
SSDs use their headroom to offer a consistent IO experience, regardless of workload. Sequential performance is easily improved by increasing platter density, buffer sizes and pushing for more aggressive prefetch in the drive's controller. As a result, the SSD advantage isn't nearly as significant. Furthermore, the new VelociRaptor delivers such a large increase in sequential speed that it's able to approach the performance of 3Gbps SSDs:.
It's because so much of client workloads are sequential in nature that some users don't really feel a dramatic difference in going from a hard drive to an SSD. The only thing I can add is that the users who are constantly frustrated by the speed of their hard drive will be the ones to most appreciate the move to solid state storage.
The other test we carried out was to copy files on each drive and once again the VelociRaptor won by a country mile. Raptor is a fast hard drive but it's annoyingly noisy and gets rather hot. All three drives have the same idle noise level - 29dBA - but when the drives start to work, the VelociRaptor sits between the Raptor and Hitachi drives in terms of noise.
The big news is the tiny power draw of VelociRaptor, which is only 4. The Crucial SSD is another story. This new technology costs a fortune and the capacity of the earliest models makes it relatively useless. Back in the real world, you'd likely need a regular hard drive to store your data files as the slow write speed of the SSD would hamper performance. Thankfully, there are new models of SSD from the likes of OCZ coming to market that offer higher capacity, lower prices and will offer a direct replacement for the hard drive.
We'll be looking at these in due course.
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