Western Digital's 640GB Caviar hard drives have found their way into each and every one of our system guides for just about two years now. We've recommended one flavor or another across a wide range of systems, including our budget Econobox, the mid-range Grand Experiment, and even the modestly opulent Sweeter Spot build. Indeed, the 640GB Caviars have been one of the best examples of the proverbial sweet spot in recent memory.
As all half-dozen or so of our female readers can no doubt attest, the sweet spot can be difficult to find. You'll know when you've found it, though. The original Caviar SE16 640GB debuted with all the right ingredients: two of the highest-density platters available at the time, a 7,200-RPM spindle speed, low noise levels, reasonable power consumption, an affordable price tag, and best-in-class performance across a diverse range of sequential, random, synthetic, and real-world tests.
For obvious reasons, the SE16 became an instant favorite among enthusiasts. Eventually, it was supplanted by the Caviar Black. Largely the same drive as the SE16, the Black doubled the cache to 32MB and bumped the warranty up to five years. And since the 640GB flavor was still a lower capacity than then-flagship terabytes, you could still get it cheap. That's like taking the sweet spot, drizzling it with chocolate sauce, and then adding bacon. Even I couldn't resist and bought two for the RAID 1 array in my personal desktop.
The uncanny ability to combine top performance with low noise levels is what really made the 640GB Caviars so special. Higher-end terabyte drives were louder at the time, likely because they needed to use three or four platters to hit the 1TB mark. 640GB only took two platters, which meant less weight for the drive motor to spin, less power consumed, and less heat generated, too.
Naturally, we've been eagerly anticipating the 640GB Caviar's spiritual successor: a two-platter Caviar Black that uses Western Digital's latest 500GB platters. This next step up the areal density ladder debuted more than a year ago inside a low-power, two-terabyte Caviar Green. Some eight months later, the very same platters spun up to a full 7,200 RPM inside the Caviar Black's shot at the 2TB mark. And now, finally, Western Digital is putting them in a two-platter Caviar Black.
Platter capacity is so important to mechanical hard drives because it plays a large role in defining overall drive performance. What really matters is the platter's areal densityhow many bits it squeezes into a given unit area. The higher the areal density, the more data the drive head can access over a given physical distance. Platters that have the same total capacity don't necessarily share the same areal density, though. For example, Seagate's Barracuda XT 2TB features 500GB platters that have an areal density of 347 Gb/in², while Western Digital's 500GB platters squeeze 400 gigabits into every square inch. Advantage, WD.
Dacking data so densely under the drive head will speed sequential transfers, but it can make seeking random sectors more difficult. To give you an idea of what kind of precision is required, consider that data points on the surface of a 3.5" platter spinning at 7,200 RPM are moving at up to the equivalent of about 120 km/h. WD's 500GB platters have a track width of roughly 100 nanometersone thousand times narrower than a human hair. The drive head, which sits at the end of an actuator arm several inches in length, must be capable of darting from track to track in milliseconds, all while flying within nanometers of the surface of the platter.
To help it track quickly in such challenging conditions, the 2TB Caviar Black employs a secondary actuator stage powered by a tiny piezoelectric motor perched at the tip of the drive arm. This second stage gives the drive head 500 nanometers of fine-tuning precision beyond what's offered by the main actuator. However, this dual-stage approach hasn't trickled down to the 1TB Black, which uses a single-stage design. Western Digital said the 2TB Black would have been slower without the dual-stage actuator, so it seems likely that some performance has been left on the table by not including it in the 1TB model.
|Maximum external transfer rate||600MB/s|
|Maximum sustained data rate||126MB/s|
|Average rotational latency||4.2 ms|
|Spindle speed||7,200 RPM|
|Areal density||400 Gb/in²|
|Idle acoustics||28 dBA|
|Seek acoustics||33 dBA|
|Warranty length||Five years|
Of course, Western Digital's own datasheets already concede that the new 1TB Black is going to be a little slower than its four-platter, 2TB cousin. The 1TB drive has a maximum sustained data rate of 126MB/s, while the 2TB model can sustain speeds of up to 138MB/s. That discrepancy might seem counter-intuitive given that the drives use the very same platters. However, the fastest area of the disk is the outer edge of the platter; the 2TB drive has twice the platters of the 1TB model and thus double the outer-edge area.
Although the new terabyte Black may not have the platter count or dual-stage actuator to challenge for the performance crown, it does have an ace up its sleeve with support for a 6Gbps Serial ATA interface. Well, maybe it's more of a joker. The fact is that the drive's 126MB/s maximum sustained transfer rate isn't even fast enough to saturate a gen-one 150MB/s SATA link, let alone the second-gen 300MB/s SATA ports present in most modern systems.
Only short burst transfers from the Black's DRAM cache memory stand to benefit from the drive's faster host interface. That cache does weigh in at 64MB, which is a lot for a mechanical hard drive. However, 6Gbps SATA support didn't do much for Seagate's Barracuda XT, which also has a beefy 64MB cache, so we don't expect much better from the Black.
I'd expect retailers to trumpet the Caviar's new-fangled SATA support from the rooftops, so it shouldn't be difficult to differentiate the drive from the old three-platter, 3Gbps Caviar Black 1TB. You can also tell the two apart based on their model numbers: the old Black is the WD1001FALS, while the new drive carries a WD1002FAEX model designation.
Like other members of the Caviar Black family, Western Digital's latest is covered by a five-year warranty. Most desktop hard drives offer three-year warranties, which is yet another reason we've been recommending the Black for all this time. A longer warranty doesn't necessarily guarantee your drive will last, of course, but if it fails, at least you'll be guaranteed a free replacement for longer.