Not so long ago, 1-terabyte hard drives cost hundreds of dollars each. And they didn't exist in the 2.5-inch form that permits the drives in this roundup to be so portable. Today, you can easily slip a 1TB unit into your pocket. Two of the drives in this roundup--Seagate's FreeAgent Go 1TB and Western Digital's My Passport Essential SE 1TB--fit a terabyte of capacity into a 2.5-inch mechanism, thanks largely to adding a third platter. The extra platter makes the units (especially the Seagate) slightly thicker and heavier than a typical 2.5-inch portable drive, but they remain highly portable just the same.
Samsung's supersmall S1 Mini--the only 1.8-inch hard drive that we tested here--had the smallest capacity in the roundup (120GB). Of the other units we tested, four offered 250GB of storage, six had 320GB, eight had 500GB, and one had 640GB, though most of them are available in different capacities.
The amount of storage you need depends on how you use the drive. If it's strictly for business documents, even the 120GB S1 Mini probably offers plenty of space. On the other hand, if you want to rip and watch your DVD collection from a hard drive, even 1TB may eventually be too little.
Western Digital's My Passport Elite includes an LED gauge on the front of the unit that tracks available capacity. Depending on how you use your storage device, this feature could be extremely handy. The drive comes with a dock, and with multiple drives in play, the gauge offers a nice way to determine which one has the most space available for your next operation or project.
Drives equipped with an eSATA or FireWire 800 bus were much faster than their USB 2.0 cousins, and eSATA was about 10 percent faster than FireWire 800. We also noticed differences in performance within each bracket. The Rocstor Airhawk A9 was the fastest of the drives we tested via FireWire 800, by 7 percent. The other three FireWire 800 drives finished within a couple of percentage points of each other. Among USB 2.0 drives, the two Western Digital My Passport models earned top marks for performance.
Most of the other drives had minor differences in test scores. Generally, 1.8-inch drives are slower than 2-inch mechanisms; so the Samsung S1 Mini's second-to-last-place finish is less surprising than its beating the Toshiba Portable Hard Drive 640GB (whose performance improves if you manually launch the included software and reformat the drive).
The type of interface you use has more influence on your portable hard drive's performance than any other factor; and vendors can replace the mechanism inside any model whenever they please.
Hard-drive manufacturers' efforts to improve the shock resistance of their bare hard drives have yielded innovations such as incorporating sensors for g-force (acceleration due to gravity) to detect when a drive is falling through space. Even so, hard drives remain too fragile to withstand even normal use without additional protective measures.
To reduce shock and vibration in hard drives, manufacturers place rubber washers at points where the drive is screwed to the enclosure and use rubberized external coatings and bumpers as high-tech slings inside the box.
The goal is to reduce the effective g-force to a level that the drive can withstand in both its nonoperational state (with its read/write heads parked safely off the disk platters) and its operational state (with the read/write heads engaged). Vendors claim that their bare drives possess a shock resistance to g-force of up to 400g when operational, and up to 1000g when nonoperational, but you should treat portable hard drives as delicate mechanisms. A drive that might survive a 3-foot fall while not plugged in would probably sustain damage if it suffered the same fall while in use.
One way to minimize your portable drive's risk of damage is to use a short cable. This helps keep the drive out of the way of flying hands and elbows, and increases the likelihood that the cable will unplug and the drive will park its read/write heads before the unit hits the floor. Drive manufacturers call this automatic action emergency retract; according to Seagate, it takes from 40 to 80 milliseconds, depending on where the heads are when power is cut off. The drive taps residual electromotive force from the spinning platters to perform the emergency operation.
Every drive in our roundup withstood the mild bumps that we subjected them to, and a couple of designs stood out for their ruggedness: Adata's bright yellow Sport SH93 and Hitachi's SimpleTough 320GB. The SH93's USB port is capped with soft rubber, and the company claims that the resulting seal can withstand immersion in 1 meter of water for 30 minutes without leaking. An integrated raceway around the SH93's rubberized waist lets you store the included cable.
The SimpleTough comes with a conveniently integrated, nonremovable cable, as does the Buffalo MiniStation Metro Portable, the CMS V2ABS, and the LaCie Little Disk 250GB. Only the SimpleTough's cable is ruggedized with a corrugated, high-grip surface, however. Hitachi claims that it's waterproof, too.