Western Digital has just released the Black2 — 2.5-inch hard drive that combines a 1-terabyte hard disk drive and 120-gigabyte solid-state drive. Curiously, though, the WD Black-squared isn’t a hybrid drive — it’s two separate drives in a single, over-priced package, sharing the same SATA interface. WD seems to be using the phrase “dual drive” but “2-in-1” and “combi-drive” are both pretty accurate. Due to this unique, SSD-riding-shotgun, non-hybrid setup, it’s not immediately clear how WD wants you to use the Black2 — nor how big the performance gains actually are. For $300, though, we have high expectations.

The Black2 is quite literally two drives in one — it’s 2.5-inch drive with a 120GB SSD strapped onto a 1TB 5400 RPM hard drive. The entire package is just 9mm tall, which is thin enough for most laptops. WD claims that the SSD portion is capable of 350MB/sec sequential read, 140MB/sec sequential write. Early benchmarks put the drive at 225MB/sec for 4KB random reads, and 122MB/sec for random reads. These are very much middle-of-the-road scores — the Samsung 840 Pro, which has been the consumer performance SSD of choice for the last year, manages 400MB/sec for 4KB random reads. The NAND itself is 20nm MLC, and it’s governed by the JMicron’s JMF667H controller.

On the hard-drive front, we’re probably looking at a fairly standard two-platter 5,400 RPM unit. The same early benchmarks suggest that performance of the hard drive portion of the Black-squared is thoroughly mediocre, too.

Normally, when you strap an SSD to a hard drive, you get a hybrid drive — a hard drive that’s accelerated by the addition of NAND flash that acts as a high-speed cache for your regularly accessed data. The idea is, you don’t need a huge (and expensive) SSD to gain the speed benefits of NAND flash — you just need enough to store the files that you use on a daily basis (operating system, drivers, web browser, documents, etc.) The idea is that firmware on the hybrid drive (HHD) decides which files to store on the flash cache, so that the speed boost occurs transparently. (See: Seagate launches new hybrid hard drive that closes the SSD gap.)

With the WD Black2, you get two separate drives — it’s entirely down to you to decide how you use the SSD. Western Digital says they opted for the dual-drive setup to silence critics who wanted more control of which data gets cached. Whether such control is worth the massive price premium, I’m not so sure — it would cost you around $160 if you bought a 120GB SSD and 1TB hard drive separately. (Read: Crucial M500: The first 1TB SSD, priced at just $0.60/gig.) If you only have a single 2.5-inch drive bay, it might be worth the extra $140, but it’ll really come down to whether your workflow makes good use of that SSD or not. I suspect it would be easier and faster to use a 256GB SSD, paired with a large external hard drive.

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