We'll kick things off with HD Tune, which replaces HD Tach as our synthetic benchmark of choice. Although not necessarily representative of real-world workloads, HD Tach's targeted tests give us a glimpse of each drive's raw capabilities. From there, we can explore which drives live up to their potential.
HD Tune lets us capture transfer rates across the entire length of the disk for some additional graphing goodness. As you can see, the VR200M offers a healthy boost in read performance versus the other mechanical drives.
The SSDs are in another class entirely, however. Both offer substantially higher average read speeds, and unlike mechanical drives, they can sustain that performance across their entire capacity. At least in theory, every flash chip in an SSD is just as fast as the one sitting next to it. With mechanical drives, the outer regions of each platter offer higher sustained throughput than the inner ones.
That theory goes out the window a little with writes, which have always been a weakness for SSDs. The Nova's write speeds oscillate in a sawtooth pattern, but it still manages to keep ahead of the VR200M, particularly as we move inward on the VelociRaptor's platters. That said, the VelociRaptor offers much better write performance than the X25-M.
The new VelociRaptor also handily beats its predecessor and the Caviar Black here, which is to be expected. I didn't anticipate seeing the VR200M post slower write speeds on the 6Gbps Marvell controller, though. As our nifty line graph illustrates, the Marvell controller starts out slower and never manages to catch up.
Next up: some burst-rate tests that should test the cache speed of each drive.
The 6Gbps controller redeems itself somewhat in HD Tune's burst tests. However, the VR200M is still a long way from eclipsing the 300MB/s limit imposed by the old Serial ATA spec.
I'd elaborate on these numbers a little more, but I'm not convinced that Microsoft's AHCI drivers are letting the drives burst as fast as they can. When initially testing with Intel's latest AHCI drivers, HD Tune reported burst speeds 16-21MB/s higher for the VelociRaptors and Caviar Black. We've also seen the X25-M G2 burst at 241MB/s in HD Tach. Apparently, it's quite difficult to make an AHCI driver that works properly with everything.
Our HD Tune tests conclude with a look at random access times, which the app separates into 512-byte, 4KB, 64KB, and 1MB tests.
With near-instantaneous access times, the SSDs easily outgun the VelociRaptor. However, the solid-state drives start to lose their luster as we access larger chunks of data. The Nova and X25-M slow by an order of magnitude when we move from 64KB to 1MB transfer sizes, although they're still well outside the VelociRaptor's reach.
The VR200M predictably leads the mechanical field, managing access times similar to the VR150M until we get to the 1MB transfer size. In that test, the new VelociRaptor is a good four milliseconds quicker than the old onethe same margin that the VR150M enjoys over the 7,200-RPM Caviar Black.
The results play out similarly on the write front, with the VR200M finding itself wedged between slower mechanical drives and faster SSDs. Interestingly, the mechanical drives have quicker access times with writes rather than reads, while the opposite is true for our SSDs. Indeed, the 1MB transfer size proves particularly problematic for the X25-M, which otherwise has the quickest access times.
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