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Our testing methods
If you're unfamiliar with The Twins, our new duo of storage test platforms, I recommend checking out this page from our recent VelociRaptor VR200M review. These systems pack potent hardware and have been furiously testing hard drives and SSDs for weeks now. Unfortunately, Intel still hasn't resolved the performance scaling issue we found in its latest storage controller drivers for the P55 chipset. As a result, The Twins are still running the Microsoft AHCI driver built into Windows 7.

Before dipping into pages of benchmark graphs, let's set the stage with a quick look at the players we've assembled for comparison. Seagate bills the Momentus XT as a "Premium Performance" product destined for everything from laptops to high-end small-form-factor PCs, which nicely leaves the door open for all sorts of interesting comparisons. We've thrown the XT into the mix against a diverse collection of alternatives, including a selection of desktop hard drives, traditional notebook drives, and a cubic assload of solid-state goodness. Below is a chart highlighting some of the key attributes of the contenders we've lined up.

  Flash controller Interface speed Spindle speed Cache size Platter capacity Total capacity
Agility 2 SandForce
SF-1200
3Gbps NA NA NA 100GB
Caviar Black 2TB NA 3Gbps 7,200 RPM 64MB 500GB 2TB
Force F100 SandForce
SF-1200
3Gbps NA NA NA 100GB
Momentus 7200.4 NA 3Gbps 7,200 RPM 16MB 250GB 500GB
Momentus XT NA 3Gbps 7,200 RPM 32MB 250GB 500GB
Nova V128 Indilinx
Barefoot ECO
3Gbps NA 64MB NA 128GB
PX-128M1S Marvell Da Vinci 3Gbps NA 128MB NA 128GB
Scorpio Black NA 3Gbps 7,200 RPM 16MB 160GB 320GB
Scorpio Blue NA 3Gbps 5,400 RPM 8MB 375GB 750GB
SiliconEdge Blue JMicron JMF612 3Gbps NA 64MB NA 256GB
SSDNow V+ Toshiba T6UG1XBG 3Gbps NA 128MB NA 128GB
VelociRaptor VR150M NA 3Gbps 10,000 RPM 16MB 150GB 300GB
VelociRaptor VR200M NA 6Gbps 10,000 RPM 32MB 200GB 600GB
Vertex 2 SandForce
SF-1200
3Gbps NA NA NA 100GB
X25-M G2 Intel PC29AS21BA0 3Gbps NA 32MB NA 160GB
X25-V Intel PC29AS21BA0 3Gbps NA 32MB NA 40GB

Given the lofty cost per gigabyte of SSDs, traditional notebook drives are the XT's closest direct competitors. Naturally, we've included the old Momentus 7200.4, which preceded the XT as Seagate's premiere mobile drive. The 7200.4 has the same 250GB platters and an identical spindle speed, but half the cache and no flash. We've also thrown in a couple of Western Digital's most relevant 2.5" mobile drives. The Scorpio Blue 750GB is the company's highest-capacity 5,400-RPM model with a standard 9.5-mm drive height, while the Black is the company's top-of-the-line 7,200-RPM offering. Western Digital doesn't yet have a 7,200-RPM notebook drive with a 500GB capacity, so we're stuck with a 320GB Black.

On the SSD front, we've collected all the relevant players, including drives based on Indilinx, Intel, JMicron, Marvell, SandForce, and Toshiba controllers. All the bases are covered with the exception of Crucial's RealSSD C300, which is powered by a new Marvell controller with a 6Gbps SATA interface. Crucial just recently released a firmware update to address serious performance issues, and now that it's out, we'll have a full review of the RealSSD soon.

Although it might not seem like a fair fight, we've thrown in results for a striped RAID 0 array built using a pair of Intel's X25-V SSDs. The X25-V only runs a little more than $100 online, and with many new gaming notebooks sporting dual hard drive bays, a mobile RAID array isn't out of the question. Our X25-V array was configured using Intel's P55 storage controller, the default 128KB stripe size, and the company's latest 9.6.0.1014 Rapid Storage Technology drivers.

Last, but not least, we've included performance data from a trio of mechanical hard drives. Western Digital's 10k-RPM VelociRaptor VR200M is the fastest mechanical hard drive that plugs into a Serial ATA interface, and with a 2.5" form factor (albeit one that's too thick for standard notebooks), it's an intriguing alternative for folks building small-form-factor rigs. Of course, plenty of SFF cases feature 3.5" drive bays, so we've thrown in the fastest 7,200-RPM desktop drive on the market, Western Digital's Caviar Black 2TB.

The block-rewrite penalty inherent to SSDs and the TRIM command designed to offset it both complicate our testing somewhat, so I should explain our SSD testing methods in greater detail. Before testing the drives, each was returned to a factory-fresh state with a secure erase, which empties all the flash pages on a drive. Next, we fired up HD Tune and ran full-disk read and write speed tests. The TRIM command requires that drives have a file system in place, but since HD Tune requires an unpartitioned drive, TRIM won't be a factor in those tests.

After HD Tune, we partitioned the drives and kicked off our usual IOMeter scripts, which are now aligned to 4KB sectors. When running on a partitioned drive, IOMeter first fills it with a single file, firmly putting SSDs into a used state in which all of their flash pages have been occupied. We deleted that file before moving onto our file copy tests, after which we restored an image to each drive for some application testing. Incidentally, creating and deleting IOMeter's full-disk file and the associated partition didn't affect HD Tune transfer rates or access times.

Our methods should ensure that each SSD is tested on an even, used-state playing field. However, differences in how eagerly an SSD elects to erase trimmed flash pages could affect performance in our tests and in the real world. Testing drives in a used state may put the TRIM-less Plextor SSD at a disadvantage, but I'm not inclined to indulge the drive just because it's using a dated controller chip.

With few exceptions, all tests were run at least three times, and we reported the median of the scores produced. We used the following system configuration for testing:

Processor Intel Core i5-750 2.66GHz
Motherboard Gigabyte GA-P55A-UD7
Bios revision F4
Chipset Intel P55 Express
Chipset drivers Chipset 9.1.1.1015
Memory size 4GB (2 DIMMs)
Memory type OCZ Platinum DDR3-1333 at 1333MHz
Memory timings 7-7-7-20-1T
Audio Realtek ALC889A with 2.42 drivers
Graphics Gigabyte Radeon HD 4850 1GB with Catalyst 10.2 drivers
Hard drives Western Digital VelociRaptor VR200M 600GB
Western Digital Caviar Black 2TB
Western Digital VelociRaptor VR150M 300GB
Corsair Nova V128 128GB with 1.0 firmware
Intel X25-M G2 160GB with 02HD firmware
Intel X25-V 40GB with 02HD firmware
Kingston SSDNow V+ 128GB with AGYA0201 firmware
Plextor PX-128M1S 128GB with 1.0 firmware
Western Digital SiliconEdge Blue 256GB with 5.12 firmware
OCZ Agility 2 100GB with 1.0 firmware
OCZ Vertex 2 100GB with 1.0 firmware
Corsair Force F100 100GB with 0.2 firmware
Western Digital Scorpio Black 320GB
Western Digital Scorpio Blue 750GB
Seagate Momentus 7200.4 500GB
Seagate Momentus XT 500GB
Power supply OCZ Z-Series 550W
OS Windows 7 Ultimate x64

We used the following versions of our test applications:

The test systems' Windows desktop was set at 1280x1024 in 32-bit color at a 75Hz screen refresh rate. Vertical refresh sync (vsync) was disabled for all tests.

Most of the tests and methods we employed are publicly available and reproducible. If you have questions about our methods, hit our forums to talk with us about them.