Four New 2.5" Hard Drives, Benchmarked

Over the past few years, 2.5" hard disk capacities have grown by leaps and bounds. And although they're still typically slower than 3.5" drives, performance in the 2.5" form factor continues to increase due to higher data density. Today, even 2.5" drives positioned as quiet energy-savers manage sequential transfer rates over 85 MB/s, while more performance-oriented disks sport transfer rates just shy of 100 MB/s.

We're adding four new drives to our 2012 Mobile Hard Drive charts: Hitachi's Travelstar 7K750 and Travelstar 5K1000, Toshiba's MQ01ABD100, and Western Digital's Scorpio Blue WD5000LPVT. Among these four models, only the Travelstar 7K750 is performance-oriented. The Travelstar 5K1000, Toshiba's disk, and the Western Digital drive are “green” offerings that focus on low noise and low power draw.

A 2.5" Hard Disk Market Survey

Of the five major hard disk brands (Hitachi, Samsung, Seagate, Toshiba, and Western Digital), there are really only three manufacturers. Hitachi’s drive division was acquired by Western Digital, and Samsung’s by Seagate. While Hitachi and Samsung disks only live on as brand names, so far the acquisitions aren't impacting the model line-ups. You can still choose among a wide variety of 2.5" repositories, including mammoth 1 TB models.

Although terabyte-sized monsters, such as the Toshiba MK1059GSM, have been available for more than two years, innovation in the 2.5" disk market has not halted. The evidence can be seen in one of our own little pet peeves: disk height. If you ordered a 1 TB drive two years ago to beef up your notebook, you might have been in for a surprise. Odds are good that the component wouldn't have fit in your notebook’s drive bay! Because the first generation of 1 TB drives typically used three 333 GB platters, their height necessarily increased to 12.5 mm, which is too tall for most mobile platforms.

500 GB Platters Allow Standard-Height 1 TB Drives

As the data density of platters increases, those problems are now surmountable. Most mobile 1 TB disks have transitioned to two 500 GB platters at a Z-height of 9.5 mm. In today's story, Toshiba's single-platter MQ01ABD100 is the density leader at 744 Gb per square inch, followed by Hitachi's Travelstar 5K1000 at 694 Gb per square inch and Travelstar 7K750 at 502 Gb per square inch.

Just because drive height compatibility issues are improving doesn't mean you should stop double-checking spec sheets before making purchases, though. Case in point, Western Digital still sells a 12.5 mm version of its 1 TB Scorpio Blue (WD10TPVT) alongside a 9.5 mm Scorpio Blue (WD10JPVT) with the same capacity.

There are other kinds of exceptions as well, like disks with a PATA interface. While parallel ATA has generally fallen out of favor, some manufacturers still offer models with this deprecated connector. For instance, Western Digital’s Scorpio Blue line-up still contains a handful of PATA-based disks. Fortunately, most mobile disks now sport at least a 3 Gb/s SATA interface. A few, such as the Hitachi Travelstar 5K1000 and Seagate Momentus XT, even support 6 Gb/s data rates.

Advanced Format is Already Ubiquitous

Achieving a 9.5 mm Z-height relies on greater data density. And while this is largely accomplished through improvements like smaller read/write heads and vertical recording, it is also partly attributable to Advanced Format (AF). AF sectors are 4 KB in size, or eight times larger than the classic 512-byte sectors. By making each sector larger, there are fewer gaps between them and less space wasted on error correction. Depending on the vendor you ask, the transition to AF is responsible for anywhere from a 7 to 11% capacity increase.

Lower-capacity disks inherently don't benefit from AF as much, and they could conceivably be built using the older legacy format if vendors wanted to do that. However, there's also a cost benefit to adopting AF. To top it off, IDEMA (the hard disk manufacturer trade group) decreed that, as of January 1, 2011, all 2.5“ and 3.5“ disks sold through the distribution channel must be AF-compliant.

AF is not just about Z-height reduction or cost savings, either. It also helped overcome the so-called 2 TB limit in 3.5" disks, whereas 32-bit-long values for partition size and logical block addresses (LBAs) would have made disks larger than 2 TB impossible.