Western Digital Black2 Dual Drive - Don't Call It a Hybrid (Updated with SSHD Performance!)

Updated on 21 Jan 2014: Originally published on the 2 Jan 2014, we have updated the article to include comparisons with a hybrid hard disk drive from Seagate. This helped us better form our opinion of the Western Digital Black2 Dual Drive and its proposition. As such, performance graphs have been updated and we have also updated the conclusion segment to include our thoughts of how the two types of drives compare before awarding our final verdict and ratings.

Two Drives in One

Falling prices of flash memory have made SSDs increasingly affordable. Right now, if you want the most bang for buck in terms of system upgrades, going from an hard disk drive to an SSD will net the most appreciable rewards - booting times will be dramatically reduce and applications will launch almost instantly.

However, despite falling prices, SSDs still cost substantially more than traditional mechanical hard disk drives. To give an example, a regular 2.5-inch 1TB hard disk drive will cost around S$110 whereas an SSD of similar capacity will set you back at least S$800.

This is a problem for notebooks who want to upgrade their storage because notebooks typically only have a single 2.5-inch drive bay, and that means users must choose between performance (SSD) or capacity (HDD).

Fortunately, Western Digital has recognize this dilemma and have recently introduced the WD Black2, a dual drive that combines an SSD and HDD into a single 2.5-inch form factor drive. Not to be confused with hybrid drives, which typically only have a small amount of onboard flash memory that acts as a cache, the WD Black2 is truly two drives in one - and recognized as such by the system. The key benefit to such a configuration is that users will be able to determine what goes onto the flash memory portion of the drive and what goes onto the hard disk drive. This is useful to more advanced users who want complete control.

Since its two drives in one, it is understandable that the WD Black2 measures 9.5mm thick, which means it might not be suitable for all notebooks. The hard disk drive is actually a regular 1TB WD Blue and the SSD drive is actually taped to it and communicates using a Marvell SATA bridge chip.

The SSD drive features 128GB of storage provided by two 64GB MLC NAND chips which are sourced from IMFT and are manufactured using a 20nm process. As for the controller, Western Digital has decided to forgo the popular choices from SandForce, Marvell and even Link_A_Media and instead opted for a controller from JMicron, specifically the 667H.

According to the specification sheet, the SSD has a sequential read and write speeds of 350MB/s and 140MB/s respectively. This is considerably lesser than most SSDs in the market today, which generally hover around the 500MB/s and 400MB/s mark for both sequential reads and writes respectively. The hard disk drive portion is a regular WD Blue drive which consists of two platters and spins at 5400rpm and has a 16MB cache.

Test Setup

The WD Black2 dual drive will be tested on our recently revamped storage testbed. The main changes are the faster Core i5-2500K processor and an accompanying Z77 motherboard which has native Thunderbolt connectivity.

• Intel Core i5-2500K (3.3GHz)
• ASUS P8Z77 Pro Thunderbolt (Intel Z77 chipset)
• 2 x 2GB DDR3-1600 memory
• MSI GeForce 8600 GTS
• Windows 7

To evaluate the WD Black2, we will be testing its SSD and hard disk drive performance and comparing it against recently tested SSDs and hard disk drives.

SSDs tested:

• WD Black2
• Crucial M500
• OCZ Vector 150
• Plextor M5 Pro Xtreme
• Samsung SSD 840 Pro
• Seagate 600

HDDs tested:

• WD Black2
• Seagate Laptop SSHD (1TB)
• Seagate Ultrathin Laptop HDD
• WD UltraSlim

Judging from the specifications that Western Digital quoted, we do not expect the WD Black2 to be able to match the other SSDs on the list. Furthermore, the WD Black2 has 128GB of flash storage whereas the rest of the drives are 240/256GB variants. However, it will be interesting to see just how competitive it is against the current crop of popular SSDs. The mainstream Crucial M500 should be its closest competitor.

Since the hard disk drive portion of the WD Black2 is essentially a WD Blue drive, it should be competitive against the recently reviewed Seagate Ultrathin Laptop HDD and WD UltraSlim, two of the newer 5mm thick drives that were just announced at Computex 2013. However, the WD Black2's key competitor in this segment is arguably the hybrid hard disk drive, which contains a small amount of onboard NAND that acts as a cache. In light of this, we have included Seagate's Laptop SSHD in our testing, which has 8GB of onboard NAND. We will be omitting Iometer from the hard disk drive testing since users who use the WD Black2 will mainly use the hard disk drive for non-performance sensitive applications or simply as a drive to store files such as music, photos and videos.

The list of benchmarks used are as follows:

• AS-SSD benchmark 1.7.4739
• CrystalDiskMark 3.0.1
• PCMark 7 (Storage suite)
• Iometer (version 2006.07.27)
• Timing Tests (Cold start, Reboot, Apps Launching)
  
   

Timing Tests

We begin with our timing tests and as you can see, the WD Black2 took a little longer than the other SSDs. However, the difference between it and the fastest drives was actually not that great, and the largest margin of difference was actually just 2.3 seconds or around 8% slower when rebooting.

Update: We also found the WD Black2 to be considerably faster than the hybrid hard disk drive. However, to put these numbers into perspective, know that while the hybrid hard disk drive took over 87 seconds to launch the entire suite of Adobe CS6 applications, a regular 7200rpm hard disk drive would take over five whole minutes to do the same.

CrystalDiskMark 3.0.1 Results

CrystalDiskMark is an easy-to-run and quick utility to use to gauge a drive’s performance. It measures sequential read and write performance and random read and write speeds of random 4KB, 4KB (queue depth 32) and 512KB data.

We did not expect the WD Black2 to be competitive against the current crop of popular SSDs, and the results backed up our predictions. Write performance, in particular, was pretty dismal as it was in some cases less than half that of the other SSDs. Read performance was much better, but still trailed the SSDs by a considerable margin. Its performance suffered the most when it came to the intensive 4k, 32 queue depth workload.

It’s hard disk drive performance was decent and easily saw off the Seagate Ultrathin Laptop HDD and was about on a par with the WD UltraSlim.

Update: Comparing the WD Black2 to the hybrid hard disk drive, it was clear that the WD Black2's SSD performance was superior to the hybrid disk drive. This is to be expected. However, if we were to look at scores in the HDD section where we tested the hard disk drive performance of the WD Black2, the hybrid hard disk drive was actually the faster drive in most instances.

SSD Results

HDD Results

AS SSD 1.7.4739 Results

AS SSD is a benchmark that uses non-compressible and completely random data. What this means is that the drives using the SandForce SF-2281 controller cannot compress the data first, which takes away one of the strong advantages of this controller. Therefore this is a useful benchmark because drives that use the SF-2281 controller don't gain an upper hand.

On the copy benchmark, the WD Black2 recorded the lowest copying speeds amongst all the SSDs. Compared to the Crucial M500, a mainstream SSD, its scores were about 25% to 40% slower. When compared to SSD luminaries like the OCZ Vector 150 and Samsung SSD 840 Pro, its copying speeds could be as little as half.

Moving on, while sequential read and write speed were poor, the WD Black’s read performance on the random 4k workload was actually competitive. For example, on the 4k workload, its read speeds of 30.12 MB/s meant it outscored the Crucial M500 (27.50 MB/s) and OCZ Vector 150 (25.64 MB/s). However, performance took a turn for the worse on the intensive 4k, 64 threads workload.

Its hard disk drive performance on AS SSD was remarkable, easily seeing off the Seagate Ultrathin Laptop HDD and was easily on a par with the WD UltraSlim.

Update: Again, we saw that the hybrid hard disk drive was no match for the WD Black2's SSD. And this was especially true when it came to handling smaller data blocks where the hybrid hard disk drive would struggle to even attain speeds of 1 MB/s. The hybrid hard disk drive scores were also no better than the WD Black2's hard disk drive, which suggests that when it came to handling random, non-compressible data, the hybrid hard disk drive's caching performance benefits are negated.

SSD Results

HDD Results

PCMark 7 Results

PCMark 7 is a benchmarking suite from FutureMark that evaluates the performance of Windows 7 machines. It tests a wide range workloads and aspects of the system ranging from computation, image and video manipulation and storage. We’ll be looking solely at the storage test here.

The WD Black2’s SSD drive managed a score of 5121, which, despite being the lowest, is actually quite comparable to the Crucial M500 and Seagate 600. If we look at the detailed breakdown, we can see that it only really fell short on the “Importing Pictures” workload.

The WD Black2's hard disk drive scored 1646 points, which was the highest, leading the second-place Seagate Ultrathin Laptop HDD by a healthy 4.5%.

Update: Interestingly, the hybrid hard disk drive performed quite admirably on PC Mark7, which attempts to simulate real world workloads and tasks. It managed a score of 3287, which was not so far off from the WD Black2's SSD score of 5121. If we were to look at the breakdown of the score and examine the raw speed figures, the hybrid hard disk drive was actually pretty close on a number of occasions. And if we were to compared the hybrid hard disk drive scores to that of other hard disk drives, it was the runaway leader.

SSD Results

HDD Results

Iometer Results (Part 1)

Lastly, we put the drives through the rigorous grind of Iometer, with different workloads and I/O queue depths. We have chosen to show results from a queue depth of 1 to 5 as this better represents the workloads a typical consumer might face.

Considering the WD Black2’s underwhelming performance thus far, we were not surprised to find that it was the worst performing drive. As seen on CrystalDiskMark and AS SSD, the SSD drive on the WD Black2 suffers from poor write performance and it was no different on Iometer as its 64k streaming write performance was particularly poor - recording just barely half the IOPs of the second-lowest performing SSD, the Crucial M500.

Update: Unsurprisingly, the hybrid hard disk drive was no match for the WD Black2 and the rest of the SSDs on Iometer, and the difference in performance is staggering, especially on the intensive "File" and "Web Server" workloads. 

Iometer Results (Part 2)

Finally, we look at the I/O response times for the workloads reported on the previous page. Expectedly, considering its performance on the earlier page, the WD Black2 record appropriately high response times. Its graphs show that it was consistently one of the slower drives.

Update: Unsurprisingly, considering the hybrid hard disk drive's poor performance on the previous page, we fully expected to see it record high response times and this was exactly what we got. Its recorded response times were many times more than that of the flash-based drives - so much so, that we had to forego presenting them in these graphs. Clearly, the hybrid drive was made to compete with traditional hard drives and not these flash-based beasts. Here's an example.

An Alternative to Hybrids

The WD Black2 is remarkable because it combines two drives into a single 2.5-inch form factor. As a result, its target market are notebook users who are seeking to upgrade their storage, specifically those who want the speed of an SSD but the storage capacity of a hard disk drive.

On a whole, the concept of the WD Black2 certainly works. However, as the benchmarks show, performance is somewhat compromised. Write performance, in particular, is particular poor; and read performance was not anything to shout about either. Nevertheless, we doubt users would be able to notice the differences in daily usage. As our timing tests show, and from our experience with the drive, the drive performed smoothly enough and launched applications almost as quickly as a high-end SSD would. Besides, the hard disk drive of the WD Black2 performed respectably, easily outscoring the Seagate Laptop Ultrathin HDD on all tests and was more than a match for the WD UltraSlim.

From a cost perspective, there is no getting around the fact that at S$459, the WD Black2 is pretty costly. If you break it down, a single high-end 128GB SSD and 1TB hard disk drive should cost just around S$290. Furthermore, consider also that the most affordable 480GB SSD is presently retailing for around S$499 - just S$40 more - while a hybrid hard disk drive from either Seagate or Toshiba will set you back around S$160. The premium is therefore considerable, and mainstream users might want to look elsewhere. However, for advanced users, whether or not the WD Black2 is worth its asking price depends very much on your own preferences and requirements.

As it is, we think that the WD Black2 is a pretty niche product for notebook users who only have a single hard disk bay and want the best of both worlds, but do not want to compromise on a hybrid hard disk drive. To elaborate, the WD Black2 trumps a hybrid disk drive in two areas: 1) more flash memory and 2) full control over what files are stored on the flash drive.

Unfortunately, without a hybrid hard disk drive in our labs as comparison, it is difficult to say if the two drives in one concept of the WD Black2 is truly superior. Therefore, we will refrain from providing ratings for the drive until we have had the chance to test a hybrid hard disk drive.

As it is, the WD Black2 is an interesting product that works as advertised. Performance might be a little underwhelming, but in practical usage, we think users would be hard pressed to notice the difference. Stay tuned as we will update this review once we have had the chance to test a hybrid hard disk drive.

Updated on 21 Jan 2014 to Factor in Hybrid Hard Drive Performance:-

To focus on just the benchmarks to evaluate both the WD Black2 and hybrid hard disk drive would be unfair to the latter. The WD Black2 is really two drives in one and in terms of benchmarks it absolutely blows the doors off the hybrid hard disk drive, which is really just a regular hard disk drive but with a larger flash memory cache.

In practical usage scenarios, the gulf in performance is not that wide. For example, on PCMark 7, which puts the drives through everyday usage scenarios, the hybrid hard disk drive managed a score of 3287 or about 35% less than the WD Black 2. However, if were to pit this against the hard disk drive portion of the WD Black 2, the hybrid hard drive actually outscored it by by close to 100%. Clearly then, a hybrid hard disk drive provides substantial performance benefits over a pure mechanical hard disk drive.

In addition, if we were to look at the timing tests, cold start timings were actually quite competitive, but reboot timings were a bit disappointing. And while it may take our hybrid hard disk drive close to a minute and a half to launch the entire suite of Adobe CS6 applications, remember that it takes a performance-grade 7200rpm hard disk drive over five whole minutes to do the same. We reckon it will take a shorter time for the hybrid disk drive if we had kept the number of apps down to a smaller number, this will enable it to make better use of its limited amount of cache capacity.

Hence, if performance is not the utmost concern for you or if your budget is limited, a hybrid hard disk drive is not a bad way to go as it offers substantial performance increases over a regular all mechanical hard disk drive. Plus it costs only slightly more than regular mechanical hard disk drives and substantially less than the WD Black2. On the other hand, if you only have a single drive bay in your notebook and you desire SSD levels of performance but do not want to sacrifice on capacity, the WD Black2 is the only viable, albeit costly, option.

However, do be sure that your notebook can accommodate drives that are 9.5mm in height; many Ultrabooks may only be able to accommodate 7mm drives or thinner. As such, the WD Black2 might not be compatible with a wide range of notebooks even if you can afford it.

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