WD has begun shipping its first 5-mm notebook drives, and there are hybrid configurations in the mix. According to the press release, the drives are the first 5-mm specimens around, giving WD a 2-mm edge over the slim 7-mm offerings already on the market. That might not seem like much of a difference, but it represents a 28% reduction. System builders trying to cram more storage into ever-thinner chassis will surely be pleased.
The 5-mm drives were designed with a "clean-sheet approach," WD says. They're based on a common mechanical platform, which employs a single 500GB platter. To improve shock tolerance, that platter is secured at both ends using Western Digital's StableTrac motor shaft. The drive employs a dual-stage actuator familiar from the firm's high-capacity desktop offerings.
On the WD Blue 5 mm, the platter spins at a sedate 5,400 RPM. Western Digital isn't divulging the spindle speed for the Black variant, but that version is a hybrid with built-in flash storage. Like Seagate's latest hybrids, the Black is labled a solid-state hybrid drive, or SSHD.
The press release is curiously bereft of information on WD's hybrid tech, but we've been able to fill in a few details. The cache uses MLC NAND and will be available in capacities between eight and 24GB. The cache can host data for both read and write requests, and cached writes are written to the platter simultaneously.
Somewhat surprisingly, there will be two versions of the Black SSHD: one with "WD proprietary" hybrid tech, and another based on "industry standard SATA I/O technology." We've asked Western Digital to elaborate on the differences between the two and whether either has specific driver, OS, or platform requirements. I suspect one implementation may be designed specifically for Intel's Smart Response Technology caching scheme; we already know Seagate has an SRT-optimized SSHD on the way for next-gen ultrabooks.
Just because the new 5-mm drives are shipping doesn't mean they'll pop up at retailers like Amazon and Newegg. The drives are going to industrial distributors and major system builders only. The Blue model doesn't even have a standard Serial ATA connector. Instead, it sports a tiny SFF-8784 connector that looks a little like the CrossFire or SLI "golden fingers" found on discrete graphics cards. This card-style interface is better suited to ultra-slim drives than existing SATA port hardware. A version of the Black could be offered with a similar connector depending on whether notebook makers demand it.
The WD Blue 5 mm has a suggested price of $89 and comes with two years of warranty coverage. Pricing and warranty information isn't available for the hybrids, but I'd expect a longer warranty. All the other drives in WD's Black family have five-year coverage.
While it's certainly impressive to see 500GB squeezed into such skinny notebook drives, I'm puzzled as to why there's so little fanfare accompanying the arrival of Western Digital's first hybrid drives. That's the world we live in, I guess—too much focus on dress size, not enough on intelligence. We may have to put these 5-mm drives through our storage test suite to see how they fare. I'm particularly interested in how the Black SSHD stacks up against Seagate's Laptop Thin SSHD, which combines 8GB of flash memory with 500GB of 5,400-RPM mechanical storage.