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 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.
At first glance, the Western Digital Black2 Dual Drive looks like a standard 2.5in hard disk. However, it’s actually two disks in one, with both a 1TB hard disk and 120GB SSD in the same shell. It’s not a hybrid drive (or SSHD) by definition like the Momentus XT because there’s no caching involved; it’s just two drives in a case with one SATA3 interface. The SSD and hard drive appear as separate partitions, giving the end-user the power to decide what data goes to the SSD and what doesn’t. The idea is that you install Windows and your programs on the fast SSD, and save the larger, slower drive for all your documents and media files. It’s for this reason Western Digital labels the Black2 as a “dual drive” rather than a hybrid drive. In a nutshell, “dual-drive” is a logical name for the drive because it’s fundamentally two drives in one.
Design & Features
The package 9mm high, so it will fit in many, but not all laptops (most newer thin-and-lights can accommodate only drives that are 7mm high). The SSD and HDD share the same drive interface, but they’re treated as separate entities, and Windows will assign different drive letters to each of them.
Conveniently, the Black2 comes with a couple of extras to help you install the drive in your computer. A USB3-to-SATA adaptor and a downloadable edition of Acronis True Image that only works with the Black2 can be used to clone your PC’s existing Windows installation to the SSD. This is a generous pack which will make upgrading a PC or laptop much easier. At 9.5mm, the drive is deeper than most SSDs or laptop hard disks, so if you planning on fitting it in a laptop check your drive bay is big enough.
You don’t need Acronis True Image if you simply reinstall Windows from scratch, but the software driver is essential, as without it only the 120GB SSD part of the Black2 will be visible to Windows. The driver is compatible with Windows 8.1 and Windows versions as old as XP. The drivers are included on a small USB flash drive.
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. This makes the Black2 unsuitable for NAS boxes and RAID. Initially the Black2 launched without driver support for Mac OSX but the necessary software has since been released. You’ll need to update the Black2’s firmware (available from support.wdc.com) to make it work. The entire process is reasonably complicated on a Mac, and setting the drive up for Windows use is certainly simpler.
Wd Black2 is 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. That makes us understand why WD quotes performance figures for the SSD of 350MB/s read and 140MB/s write through the SATA 6Gb/s interface. Compared to modern dedicated SSDs these numbers are well below industry norms, but that’s attributable largely to the split interface limitation in the WD Black2 architecture. WD does not quote performance figures for the HDD portion of the drive, however they should be in line with the Blue Slim HDD.
Breaking down the two components, WD is using a 5400RPM 1TB hard drive (WD Blue Slim) that takes up most of the physical space. Glued on top and bridged via the controller chip, is a 120GB SSD that’s powered by a JMicron controller. This obviously marks the first SSD effort WD has embarked on since their unsuccessful attempt with the SiliconEdge SSDs in early 2010.
Understanding exactly what the Black2 is, is critical to understanding where WD hopes it will play in the market. This is of course a drive designed for the mobile market; specifically full size notebooks that house a 9.5mm drive bay. The addressable market is actually smaller than that though; it’s really just notebooks that have the 9.5mm drive bay and no other expansion options for an SSD via second drive bay, mSATA slot or removable optical drive bay (should the user decide to remove it for storage). WD is banking that many users would appreciate the simplicity of a single drive sandwich solution, but as this is targeted largely to enthusiasts, market acceptance for the design will be the deciding factor in the success or failure of the Black2 idea. Beyond just the hardware adoption challenges though, WD only supports Windows with this release. As a result, Mac users are entirely left out, slicing off a good number of the enthusiasts WD hopes to attract.
The WD Black2 is backed with five-year limited warranty which has become the standard warranty term for enterprise-class drives.
You can download the official specification sheet from Western Digital’s website here.
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.
According to PC World magazine, the drive delivers decent performance in every aspect aside from its SSD write performance, which is disappointingly slow. In the test run on the drive in the magazine’s laboratory, it could write 10GB collection of small files at just 150MBps, and it wrote a single 10GB file at only 151.1MBps. That’s faster than most mechanical hard drives, to be sure, but the testing team had to dig all the way back to an obsolete Corsair Force drive with asynchronous NAND to fine a slower-writing SSD.
The test result ended up that Black2’s SSD read performance was a little closer to what’s expected: 362.5MBps for 10GB collection of small files, and 362.1MBps for a single 10GB file.
As for Storage Review team, after testing each drive individually, they attempted to hit both drives at the same time to see what happens when the Marvell traffic cop controller gets stressed. When both drives received read or write activity, they were responsive, but performance drops if both devices are accessed at the same time where individual speeds would measure in excess of 500MB/s. This means if the SSD can offer read speeds of 450MB/s and the HDD 110MB/s read, total performance will never exceed the limit of a SATA 6Gb/s port. In early tests when the drives received opposite workloads however, the tests locked up indicating that the controller may not be able to handle multiple streams of conflicting read/write activity in certain scenarios. Rebooting the system and reinstalling the drivers which recreated the partition mapping did resolve the issue, but it’s worth noting that the drive failed to perform as it should under our testing scenario. WD acknowledges that future firmware releases will continue to enhance the stability and performance of the product, so it’s possible that multi-drive performance will improve over time.
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.
There are two conditions in which the Black2 makes sense:
1) You have a laptop with a single 2.5″ hard drive bay and no mSATA slot. Check also other hybrid hard drive options in our picks for best laptop SSHD.
2) You need more capacity than 480/512GB and/or aren’t willing to pay for a 500GB class SSD.
If your answer to both questions is a ‘yes’, the Black2 is likely the best option in the market right now. However, if you answered ‘no’ to either of the questions, there are far better and cheaper options available.
If your laptop can take two 2.5″ drives or a 2.5″ drive and an mSATA SSD, it’s much cheaper to go that route. As the table below shows, a 120GB SSD and a 1TB 2.5″ hard drive costs almost half of what the Black2 does.
By buying separate drives you are also given the option to choose the SSD and HDD in case you want a higher performance SSD or prefer a certain brand HDD. Even if you went with a high-end SSD like the 120GB SanDisk Extreme II, you would end up saving over $50. In fact you could easily buy a 240GB SSD and still easily beat the Black2 in price.
If there is one thing WD should have done in the Black2, that would be caching (or tiered storage). The reason why people usually have negative thoughts about caching is because the solutions are always crippled by small, low performance SSDs. The Black2 has enough NAND to make the caching experience smooth and with the right software the Black2 could have been similar to Apple’s Fusion Drive.