The value perspective
Still with me? Congratulations, you've reached our famous value analysis, which adds capacity and pricing to the performance data we've explored over the preceding pages. We used Newegg prices to even the playing field for all the drives, and we didn't take mail-in rebates into account when performing our calculations.
First, we'll look at the all-important cost per gigabyte, which we've obtained using amount of storage capacity accessible to users in Windows.
Obviously, the mechanical drive is in another class here. But ignore that for a moment and count just how many of the SSDs have reached the dollar-per-gigabyte mark... plus some change. On capacity alone, the Force 3 looks like the best deal of the lot, followed closely by the Agility 3, m4, and Performance 3 series.
Our remaining value calculations require a single performance score, which makes things a little complicated. We've come up with an overall index that normalizes SSD performance against a common baseline provided by the Caviar Black. This index uses a subset of our performance data, including HD Tune's random 4K response times and average transfer rates, our used-state FileBench results, scores from all five DriveBench 1.0 workloads, mean DriveBench 2.0 service times plus the percentage above 100 ms, IOMeter transfer rates for each access pattern with eight outstanding I/O requests, the Windows 7 boot duration, and our load times in Portal 2 and Duke Nukem Forever.
Time constraints prevented us from using a slower baseline drive than our Caviar Black, which actually scored better than a few of the SSDs in a couple of DriveBench metrics. To prevent those scores from jacking with the overall results, we've fudged the numbers slightly to match our mechanical baseline. Calculating overall performance scores is an imperfect science, and I may have to dust off our old 4,200-RPM notebook drive to set a new baseline for future reviews.
We've been using a harmonic mean to generate our overall score for storage performance because it does a good job of handling normalized results that can vary by several orders of magnitude from one test to the next. After much reading on the subject and calculating numerous performance scores in previous storage reviews, we're convinced this is the best approach for our particular mix of tests.
We have a healthy habit of zeroing our graphs here at TR, but I guess this one could start at 100%, which represents the overall performance of our Caviar Black hard drive. Everything above that mark is gravy, and the synchronous SandForce drives are comfortably in the lead. The Vertex 3, Force GT, and HyperX are clearly superior to their asynchronous counterparts overall.
Although slower than the leaders, the Agility 3 and Force 3 manage to stay ahead of the rest of the field. The Crucial m4 isn't far behind, relegating the Intel drives and the Performance 3 to the back of the pack.
So, what happens if we mash this overall performance score with cost and capacity? Magic! Or, rather, performance per dollar per gigabyte, which is divides each SSD's overall score by its cost per gigabyte. We'll express this value metric as a single score in a line graph before exploring the relationship between performance and cost-per-gigabyte in a scatter plot.
Our three synchronous SandForce configs occupy the upper tier on the performance axis, but the lower price tags attached to the Force GT and Vertex 3 make those drives more attractive than their HyperX counterpart. The Force 3 is considerably cheaper than all of the synchronous SandForce SSDs—and its asynchronous Agility 3 twin. However, it's also quite a bit slower than the synchronous stuff.
Although this analysis is helpful when evaluating SSDs on their own, what happens when we consider the cost of drives in the context of a complete system? To find out, we've divided our overall performance score by the sum of our test system's components (which total around $800 at Newegg before adding the SSDs).
As usual, the scatter plot gives us more useful information than the bar graph. Here, we see just how small the price differences are between some of the drives. The synchronous SandForce SSDs don't cost that much more than cheaper alternatives when one takes into account the cost of a complete system.
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