To date all the hybrid storage solutions we have seen have been rather limited. Seagate got the idea right with the Momentus XT but having only 8GB of NAND (4GB in the first generation) limited the gains of caching dramatically. There simply wasn't enough NAND cache to fit all the data that users frequently used. Sure it was better than a traditional hard drive but the experience was far away from the real SSD experience. I'm actually surprised that there hasn't been any major evolution in the hybrid market -- the original Momentus XT was released over three years ago and fundamentally the current third generation Momentus XT is very similar. Back then I would've expected more and better offerings to be released within a year but obviously that hasn't happened. Until now.

WD Black2 combines a 120GB SSD and a 1TB 5400rpm hard drive into one 2.5" 9.5mm solution. WD doesn't actually call the Black2 a hybrid drive, but a dual-drive because the the SSD and hard drive are completely separate. In other words, the drive will appear as two separate volumes: 120GB SSD and 1TB hard drive. There's no caching involved and the end-user can decide what goes to the SSD as if it were a standalone drive. By default only the SSD portion is usable but WD supplies a USB drive with drivers in the retail package to make the hard drive portion visible to the OS as well. All Windows versions from XP and up are supported but there is no OS X support at the time of launch.

WD Black2 Specifications
Interface SATA 6Gbps
Sequential Read 350MB/s
Sequential Write 140MB/s
Power Consumption 0.9W (idle/standby) / 1.9W (read/write)
Noise 20dBA (idle) / 21dBA (seek)
Warranty 5 years
MSRP $299

The performance specs above are for the SSD part. Unfortunately WD wasn't willing to disclose any hardware details about the SSD other than that it uses 20nm NAND but we will find out the details once our review sample arrives this week. I was, however, able to get the information that WD worked with a partner to bring the Black2 to the market and that partner wasn't SanDisk (which was my first guess due to their prior partnership in hybrid drives). The actual hard drive spins at 5400rpm and consists of a single 1TB platter but WD didn't release any separate performance data for it. When the hard drive isn't in use, it can spin down to reduce power consumption, although 0.9W is still fairly high compared to most SSDs. 

Update: Techreport has already received their sample and opened it up, which revealed JMicron's JMF667H controller. We don't have any prior experience with the controller but generally JMicron's controllers have not been the greatest but it's been years since we've tested a JMicron based drive so things might have changed.

Update 2: WD initally told us that the drive is a single-platter design but they've now corrected their earlier statement. The hard drive consists of two 500GB platters as some of you suspected in the comments.

Given that most laptops only have room for one 2.5" drive by default, I do see a potential market for the Black2. In the past consumers have had to make the choice between a fast but small SSD or a large but slow hard drive. The Black2 eliminates the need to do that compromise. However, I'm disappointed for the lack of caching support. WD told us that they conducted market studies and according to those end-users wanted full control of the SSD and data. I don't completely agree because the reason why most consumers have negative thoughts about caching is because the available cache sizes are just way too small. Apple is the only one who has done it right with Fusion Drive by not going any smaller than 128GB, while others are trying to get by with 8-32GB. The Black2 has enough NAND for a pleasant caching experience, so not including caching software is a letdown. Technically you could use third party caching software but I still would have hoped for a solution from WD, preferably something user-configurable so it's not forced like in the Momentus XT.

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  • Subyman - Tuesday, November 26, 2013 - link

    I read that portion as a USB interface as well for some reason. To completely clarify, the author means the drivers are included on a thumb drive, correct?
  • silenceisgolden - Monday, November 25, 2013 - link

    Looks like WD asked the wrong questions in that caching study. There are a lot of places I'd like to use this drive in, but can't justify the purchase with no caching and a higher price.
  • Mayuyu - Monday, November 25, 2013 - link

    I'd say they ask the wrong people. They might have surveyed a bunch of enthusiasts.
  • shank15217 - Monday, November 25, 2013 - link

    Your assessment of Apple's fusion drive is incorrect. The fusion drive feature is a type of tiered storage, not caching. Windows Server 2012 R2 has a similar feature in storage spaces. Linux will have something similar very soon called hot data tracking through it's vfs layer. WD is correct, this can be handled easily in software, they laid the foundation now it's time for MS at all. to use it properly.
  • Kristian Vättö - Monday, November 25, 2013 - link

    Tiered storage and caching often go hand-in-hand. Caching requires a tiered storage setup but you can have tiered storage without caching or any software assistance. Fusion Drive is caching too because there's only a single volume and the software takes care of the data placement.
  • ATimson - Monday, November 25, 2013 - link

    Fusion Drive isn't caching - if it were caching, the SSD would have copies of the original data. Instead, OS X actually moves the files over.
  • solipsism - Monday, November 25, 2013 - link

    It has both. They put oft used files on the SSD and less used as well as files that wouldn't benefit from the fast reads of the SSD on the HDD. The portion of the SSD is also dedicated to caching which means anything in the cached area of the SSD could also be on the HDD (there is no need to duplicate it on the SSD). This is all configurable with CoreStorage and handled intelligently by the OS. It really is the best of both worlds.
  • tuxRoller - Wednesday, November 27, 2013 - link

    Linux currently has two different caching methods: dm-cache and bcache. Both have been merged for a few releases now.
    Additionally Facebook released flashcache awhile back which is a simple kernel module that does write through caching.
  • XZerg - Monday, November 25, 2013 - link

    By default only the SSD portion is usable but WD supplies a USB drive with drivers to make the hard drive portion visible to the OS as well.

    you have "drive" and "drivers" switched - WD supplies a USB driver with the drive to make...?
  • Kristian Vättö - Monday, November 25, 2013 - link

    Nope. There's a small USB drive included in the retail package that has drivers for the Black^2 drive. By default only the 120GB SSD is accessible and the drivers are needed to make the 1TB HD accessible as well.

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