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WD Black 2 Dual-Drive SSD+HDD Hybrid Review
Date: Dec 10, 2013
Author: Marco Chiappetta
Introduction and Specifications

Solid state drives continue to be all the rage, due to their durability, silence, and high performance versus traditional hard drives, with spinning magnetic media. And while SSD prices have dropped significantly this past year, they remain relatively expensive in terms of cost per gigabyte, and are still many times the price of a hard disk drive.

The price disparity between solid state and hard disk drives often forces mobile and small form factor users into the unenviable position of choosing performance over capacity. Provided they’ve got the budget, desktop users needn’t compromise, because their systems can accommodate multiple drives of different form factors without issue. But SFF and mobile systems are usually outfitted with only a single 2.5” drive bay, so if you want the performance of an SSD, but need a large capacity drive, you’ve got to shell out big bucks for a high-capacity SSD or settle for the lower performance of a hard drive.

WD recently released a totally new class of product that aims to resolve this conundrum, however. The new WD Black 2 Dual-Drive (SSD + HDD) pairs 120GB of solid state storage with a 1TB hard disk, in a single 2.5” drive. The WD Black 2 is not a caching solution, though, like some other hard drives outfitted with flash memory. Rather, the WD Black 2 operates as two independent drives—a fast SSD for your OS and most commonly used apps and a large hard drive for bulk storage.

The WD Black 2 SSD + HDD

WD Black 2
Specifications & Features

WD Black 2 - Currently $299 on Amazon

The WD Black 2’s full specifications are listed in the table above. As you can see, it’s a 2.5” drive (with a 9.5mm Z-Height) and it sports a SATA 6 Gb/s interface.

The SSD portion of the drive is rated for 350MB/s reads and 140MB/s writes, which are relatively low numbers by today’s standards for an SSD. They’re much higher than any hard drive, though, and of course access times on the SSD are simply in a different league versus an HDD. The SSD is built around a JMicron JMF667H controller and NAND is 20nm MLC. The 1TB hard drive’s specs aren’t listed, but as you’ll see a little later, it’s a rather speedy, single-platter 5400RPM drive, with 16MB of cache (average latency - 5.5ms), that regularly hits over 110MB/s.

To call the WD Black 2 a “dual-drive” as WD’s materials do, is somewhat if a misnomer. Yes, the drive has distinct solid state and magnetic media, but the WD Black 2 is actually recognized by a system as a single device. Out of the box, WD ships the Black 2 with the SSD portion already partitioned. This way, users know that their OS and apps are definitely installed on the fastest part of the drive. Users must run a utility which unlocks and reveals the 1TB portion of the drive. Contrary to what you may be thinking, there are no drivers or services that need to be run on the PC for the WD Black 2. Once that HDD partition is unlocked, it’s ready to go and can be manipulated as any other partition could. In fact, you could even manually repartition the WD Black 2 as one big drive, but you’ll see off behavior like this:

You see, once you travel across the solid state storage and into the magnetic media, performance drops off quite a bit. Should you accidentally screw up the partitions, users can also re-run the WD utility to hide the HDD portion of the WD Black 2 again, re-configure the SSD and start over.

The WD Black 2 and its Accessory Bundle

Included with the WD Black 2 is the drive itself, a USB to SATA adapter, a flash drive which will automatically direct users to the download the unlocking utility, a user’s guide and warranty papers.

Test Setup, IOMeter 1.1 RC

Our Test Methodologies: Under each test condition, the Solid State Drives tested here were installed as secondary volumes in our testbed, with a standard spinning hard disk for the OS and benchmark installations. Out testbed's motherboard was updated with the latest BIOS available as of press time and AHCI (or RAID) mode was enabled. The SSDs were secure erased prior to testing, and left blank without partitions for some tests, while others required them to be partitioned and formatted, as is the case with our ATTO, PCMark 7, and CrystalDiskMark benchmark tests. Windows firewall, automatic updates and screen savers were all disabled before testing. In all test runs, we rebooted the system, ensured all temp and prefetch data was purged, and waited several minutes for drive activity to settle and for the system to reach an idle state before invoking a test.

HotHardware Test System
Intel Core i7 and SSD Powered

Processor -

Motherboard -

Video Card -

Memory -

Audio -

Hard Drives -


Hardware Used:
Intel Core i7-2600K

Asus P8Z6-V Pro
(Z68 Chipset, AHCI Enabled)

NVIDIA GeForce GTX 285

4GB Kingston DDR3-1600

Integrated on board

WD Raptor 150GB (OS Drive)
OCZ Vector 150 (120GB, 240GB)
WD Black 2 (120GB + 1TB)
OCZ Vector (256GB)
Samsung 840 EVO (250GB)
OCZ Vector 450 (240GB)
SanDisk Extreme II (480GB)

OS -
Chipset Drivers -
DirectX -

Video Drivers

Relevant Software:
Windows 7 Ultimate SP1 x64
Intel, iRST 10.5.1027
DirectX 11

NVIDIA GeForce 275.33

Benchmarks Used:
IOMeter 1.1.0 RC
HD Tune v4.61
ATTO v2.47
CrystalDiskMark v3.01 x64
PCMark 7
SiSoftware Sandra 2012

I/O Subsystem Measurement Tool

As we've noted in previous SSD articles, though IOMeter is clearly a well-respected industry standard drive benchmark, we're not completely comfortable with it for testing SSDs. The fact of the matter is, though our actual results with IOMeter appear to scale properly, it is debatable whether or not certain access patterns, as they are presented to and measured on an SSD, actually provide a valid example of real-world performance for the average end user. That said, we do think IOMeter is a reliable gauge for relative available throughput within a given storage solution. In addition there are certain higher-end workloads you can place on a drive with IOMeter, that you an't with most other storage benchmark tools available currently.

In the following tables, we're showing two sets of access patterns; our custom Workstation pattern, with an 8K transfer size, 80% reads (20% writes) and 80% random (20% sequential) access and IOMeter's default access pattern of 2K transfers, 67% reads (34% writes) and 100% random access.

The WD Black 2 SSD offers consistent performance in the access patterns we tested, but it trailed the standalone SSDs by a significant margin.

In terms of actual transfer rates, the WD Black 2 also trails the other drives we tested, though it is in the same league as the SanDisk drive here.

SANDRA and ATTO Disk Benchmark

Next we ran SiSoft SANDRA, the the System ANalyzer, Diagnostic and Reporting Assistant. Here, we used the Physical Disk test suite and provided the results from our comparison SSDs. The benchmarks were run without formatting and read and write performance metrics are detailed below.

SiSoft SANDRA 2012
Synthetic HDD Benchmarking


According to SiSoft SANDRA's physical disk benchmark, the WD Black 2 SSD offers strong read performance, but its write speed trails the other SSDs significantly.

ATTO Disk Benchmark
More Information Here: http://bit.ly/btuV6w

ATTO is another "quick and dirty" type of disk benchmark that measures transfer speeds across a specific volume length. It measures raw transfer rates for both reads and writes and graphs them out in an easily interpreted chart. We chose .5kb through 8192kb transfer sizes and a queue depth of 6 over a total max volume length of 256MB. ATTO's workloads are sequential in nature and measure raw bandwidth, rather than I/O response time, access latency, etc.


Because the ATTO Disk Benchmark requires that drives be partitioned and formatted, we're able to test the performance of both the WD Black 2's SSD and HDD. As you can see, the SSD portion of the drive offers decent performance in the read tests, but still trails the standalone SSDs. In the write test, the WD Black 2 is way behind.  The HDD performs relatively well, however, and consistently offered transfer speeds over 110MB/s, once block sizes exceeded 8K.

HD Tune Benchmarks
EFD Software's HD Tune is described on the company's web site as such: "HD Tune is a hard disk utility with many functions. It can be used to measure the drive's performance, scan for errors, check the health status (S.M.A.R.T.), securely erase all data and much more." The latest version of the benchmark added temperature statistics and improved support for SSDs, among a few other updates and fixes.

HD Tune v4.61
More Info Here: http://www.hdtune.com

The WD Black 2's SSD trailed the standalone SSDs once again, according to HD Tune. Note, that we were not able to run this test on the HDD portion of the WD Black 2 due to the drive's configuration. (You can't enable the HDD and still have the drive un-partitioned. If you enabled the HDD portion and delete all partitions, it appears as a single 1.12TB drive to the OS).

CrystalDiskMark Benchmarks

CrystalDiskMark is a synthetic benchmark that tests both sequential and random small and mid-sized file transfers using incompressible data. It provides a quick look at best and worst case scenarios with regard to SSD performance, best case being larger sequential transfers and worse case being small, random transfers.

CrystalDiskMark Benchmarks
Synthetic File Transfer Tests

The WD Black 2 offered middling performance in the 4K and 512K tests, but trailed the other drives in the 4K QD32 and large sequential transfer tests.

AS-SSD Compression Test

Next up we ran the Compression Benchmark built-into AS SSD, an SSD specific benchmark being developed by Alex Intelligent Software. This test is interesting because it uses a mix of compressible and incompressible data and outputs both Read and Write throughput of the drive. We only graphed a small fraction of the data (1% compressible, 50% compressible, and 100% compressible), but the trend is representative of the benchmark’s complete results.

AS SSD Compression Benchmark
Bring Your Translator: http://bit.ly/aRx11n

The WD Black 2's SSD performance is not affected by the compressibility of the data being transferred to and from the drive. Performance is flat and consistent across the board here. Though, as expected, transfer rates are lower than the other drives once again.

PCMark 7 Storage Benchmarks
We really like PCMark 7's Secondary Storage benchmark module for its pseudo real-world application measurement approach to testing. PCMark 7 offers a trace-based measurement of system response times under various scripted workloads of traditional client / desktop system operation. From simple application start-up performance, to data streaming from a drive in a game engine, and video editing with Windows Movie Maker, we feel more comfortable that these tests reasonably illustrate the performance profile of SSDs in an end-user / consumer PC usage model, more so than a purely synthetic transfer test.

Futuremark's PCMark 7 Secondary Storage

In the trace-based PCMark 7 benchmarks, which are a better indicator of real-world performance than the synthetic transfer tests in our opinion, the WD Black 2 is competitive with the standalone SSDs, though it still trails the pack by a few percentage points.

Our Summary and Conclusion

Performance Summary: The WD Black 2 isn’t a barn burner, as our benchmarks have shown. To squeeze a 120GB solid state drive and 1TB hard disk drive, into a single 2.5” device, with 9.5mm Z-Height, WD had to make some obvious concessions. Don’t let the synthetic numbers fool you, though. In the trace-based PCMark 7 storage benchmarks, which are a better indicator of real-world performance, the WD Black 2 trails faster, standalone SSDs by only a few percentage points. The WD Black 2 offers the same responsive, and speedy performance SSD users have some to expect.

The WD Black 2 SSD + HDD Dual Drive - Currently $299 on Amazon

WD deserves some kudos for bringing a product like the Black 2 to market. The drive is obviously not for everyone. Desktop users would save a few bucks and be better served by separate solid state and hard disk drives. All-in-One, small form factor, or mobile users, with systems that have only a single 2.5” drive-bay, however, no longer have to compromise between speed and capacity. With the WD Black 2, users can enjoy the benefits of an SSD and still have plenty of bulk storage space at their disposal.

This level of integration comes at a premium, though. WD is currently selling the Black 2 Dual Drive for $299, or roughly $0.28 per gigabyte. That’s way more affordable than any decent standalone solid state drive at the moment, but about the double (or more) than some hybrid drive or standard hard drives. Whether or not the WD Black 2 is a good fit for your needs is going to depend on your type of systems and budget, but there’s no way you’re going to get a similar capacity SSD in that price range. With that said, 480GB solid state drives are available for about the same price as the Black 2, so weigh you options and capacity needs carefully.


  • Innovative Design
  • SSD Performance, HDD Capacity
  • "Just Works" - No drivers or caching software necessary
  • Price Premium
  • SSD Not Terribly Fast
  • Must "Unhide" HDD at first

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