Ever since NAND Flash began to take off, customers on a budget or with limited drive storage have had to make a choice between small pools of solid-state storage and larger, far slower, mechanical drives. The Western Digital Black2 Dual Drive($89.99 at Amazon)(Opens in a new window) is the company’s first foray into the world of hybrid storage—products that combine solid stage and spinning media (typically referred to as an SSHD). In theory, this approach offers the best of both worlds—an ultra-fast NAND drive and a larger, 1TB magnetic storage pool behind it. In practice, there are some rough spots in the implementation.

There are four basic ways to implement a hybrid drive. The first is to use caching software to dynamically load frequently-used data on a small slice of NAND flash that’s effectively invisible to the end user. The user only sees the single mechanical hard drive; all of the software-level caching happens deep in the operating system. This is the approach used by Nvelo (now a property of Samsung) and by Intel’s Smart Response Technology. The second approach is Apple’s Fusion Drive, where the operating system manages the SSD and the hard drive as a single unit. Available storage is the total of the two drives.

Both of these approaches require two different drives and two different drive bays, which is why you don’t see them much in mobile hardware. The next approach is Seagate’s Momentus/Laptop Thin product line, which uses a very small amount of onboard NAND flash to provide a buffer for a spinning disc. In this case, the amount of NAND is small, typically around 8GB.

The Black2 is something different from all of these. While it keeps the combined form factor of the Seagate drives, and packs both NAND and HDD into a 7mm 2.5-inch form factor, it has far more flash memory than your typical hybrid drive. A full 128GB of NAND flash are built into the Black2, with 8GB of the total reserved for overprovisioning. The 1TB of storage, meanwhile, is entirely separate from the rest. There’s no included caching software for managing the two drives as a single unit, and no mechanism for caching the files you use most on the SSD.

Similar Products

4.0

Excellent

Samsung 840 Series 250GB

$378.89

Check Stock

at Amazon

(Opens in a new window)

Read Our Samsung 840 Series 250GB Review

4.0

Excellent

SanDisk Extreme II 480GB SSD

$191.81

Check Stock

at Amazon

(Opens in a new window)

Read Our SanDisk Extreme II 480GB SSD Review

4.0

Excellent

Seagate 600 SSD

$198.65

Check Stock

at Amazon

(Opens in a new window)

Read Our Seagate 600 SSD Review

This is a drive that’s designed to offer flexibility of a separate solution in a single form factor. That’s an interesting idea, and Western Digital goes all out on the packaging and presentation of the unit. The box includes a USB 3.0 adapter for the Black2, the unit itself, a paper USB card with a link to download the system software (but oddly, not the software itself). Everything is boxed and packaged neatly.

Unfortunately, there are some current limitations with the software design. When you hook the drive up, the OS will only see the SSD; the HDD isn’t accessible unless you install the WD software, and it’s currently not compatible with storage drivers from ASMedia or Nvidia. There’s only one SATA port for the two drives, so accessing both simultaneously will take a performance hit compared to using two standard drives, each with its own SATA connection to the motherboard.

Performance
One of the aspects to the Black2 that makes performance evaluation tricky is that the SSD and HDD present two different operating environments with their own distinct characteristics. We’ve compared the Black2 against a standard Samsung 840 EVO SSD, Seagate’s Laptop Thin SSHD, and a 7,200rpm conventional mobile drive. These last are increasingly difficult to come by, but performance is modestly better than a standard 5,400rpm spinner.

We tested all of the drives using an Asus P877V-Deluxe motherboard with 8GB of DDR3-1600 and an Intel Core i7-3770K CPU. The P877-V Deluxe offers multiple SATA controllers from Intel and Marvell; all of the drives were connected to Intel’s 6G SATA port. In AS-SSD’s sequential and 4K tests, the Samsung 840 swept the WD Black2. The gap wasn’t so large in the sequential read test, where the WD Black2 put up a score of 427MBps compared to 506MBps for the Samsung 840 Evo, but the Western Digital SSD’s write speed of 122MBps was dwarfed by the Samsung drive’s 492MBps. The 4K 64 thread tests were little better—the Black2 turned in respectable budget SSD scores of 216MBps read and 80MBps write respectively, but the 840 EVO hit 330MBps read and 298MBps write.

The Black2’s hard drive acquitted itself somewhat better. Its sequential read speed of 111MBps was competitive with the 7,200rpm Seagate’s 109MBps and beats the Seagate SSHD’s 77MBps. Sequential write speed on the Black2 was significantly lower, at 61.4MBps, compared to 93MBps for the 7200 RPM Seagate and 103MBps for the Seagate Laptop Thin. The 4K 64-thread tests aren’t particularly applicable for conventional hardware—the drives all struggle to reach even 2MBps and mostly score below 1MBps.

AS-SSD contains a real-world file copy test with three presets—ISO files, program files, and game files. Each type of file is a different size and includes a different amount of compressible data. We reboot

in between benchmark runs of this test and throw out the outliers to prevent data caching in Windows or on-drive from polluting the results.

The Black2’s SSD portion hits respectable copy speeds of 292MBps in the ISO test, 130MBps for mid-size program files, and 181MBps for game files, all of which are neatly beaten by the Samsung 840 Evo’s 353MBps (ISO), 211MBps (Programs) and 291MBps (Gaming). The hard drive section of the Black2’s performance actually lands midway between the 7,200rpm and the Samsung Laptop Thin in ISO file copy speed (58MBps for the Black2, compared with 67 MBps for the Seagate 7,200rpm and 42 MBps for the hybrid SSHD.) It wins the Program tests outright (44MBps vs. 35MBps vs. 22MBps) and the Game copy test as well (53 MBps to 43MBps to 25MBps.)

Next, we have PCMark 7. The benchmark uses real storage workloads created by recording traces of hard drive activity when playing games, loading music or video, or copying files. These traces are used to measure the performance of storage products in comprehensive real-world scenarios. The Samsung 840 EVO takes the lead with a 5445, compared to a 5049 for the WD Black2. The hard drive portion of the Western Digital drive scores a 1602, compared to 1703 or the faster Samsung 7,200rpm drive and a 3232 for the SSHD.

The Black2 performs like exactly what it is—a budget 120GB SSD attached to a 1TB hard drive. The mobile form factor and combined option is nifty, and the entire package might even be called attractive, except for one thing: It retails at $299. At that price point, the entire offer falls apart. NAND flash drives with 400GB of capacity and much higher performance start at around $300, while a combination 256GB NAND internal and small external drive can be had for less than $300.

Western Digital appears to have banked on the convenience as a critical advantage, but the overwhelming majority of users can get by on 256GB of storage (for less money) or roughly 400GB for $10 more. If Western Digital gives the drive a price cut to $199, or bumps the amount of onboard flash to 256GB, the Black2 could make good sense. As it stands, there are too many better alternatives.