Portable hard drives: A terabyte in your pocket

Good things come in small packages — and when it comes to storage, the saying couldn't be more true. No matter what size your data set is, you can find a stylish, pocketable wonder of modern miniaturization to store it and transport it.

All portable storage units do basically the same thing, but these days they come in more flavors than you'll find at Baskin-Robbins. PCWorld Labs tested 22 models, from the credit-card-size Samsung 120GB S1 Mini to the latest capacious yet svelte 1TB Seagate FreeAgent Go and Western Digital My Passport Essential SE 1TB drives. We tested dockable models, ruggedized units, and multiple-interface units that can connect to almost any PC. Many of them came with surprisingly capable customized software packages that pop up the minute you attach the drive.

There's something for everyone; and some of the test results we obtained will surprise–if not delight–PC fans. For a ranked chart of the most outstanding models we examined, see “Top 10 Portable Hard Drives”; for a list of all 22 models we tested, together with bottom-line assessments, see “Lab-Tested: Portable External Hard Drives.”

Multiple Interfaces

Our lineup of drives includes models from Adata, Buffalo Technology, CMS, Hitachi, HP, Iomega, LaCie, Rocstor, Samsung, Seagate, Toshiba, Verbatim, Western Digital, and WiebeTech. Of the 22 drives we tested, 17 exclusively use the USB 2.0 interface. Most of those 17 have a mini-USB port, but the Western Digital models use micro-USB connectors (most often found on cell phones).

Five drives have FireWire 800 or 800/400 interfaces as well as USB 2.0, and the WiebeTech ToughTech XE Mini has an eSATA port, too. Though it offers tremendous speed, eSATA remains rare on portable drives. The Airhawk, Rocport, and SureFire models are termed triple-interface drives while the Wiebe­Tech is called a quad-interface drive.

Models with extra interfaces tend to cost a bit more, but dual-interface USB/FireWire 400, triple-interface USB/FireWire 400/FireWire 800, and quad-interface USB/FireWire 400/FireWire 800/eSATA drives behave better under many circumstances and deliver superior performance when connected via something other than USB.

Depending on the test, the eSATA-based Wiebe­Tech ToughTech XE Mini and the FireWire 800-linked Rocstor Rocbit FX KT, Rocstor Airhawk A9, Rocstor Rocport ID9, and Io­­mega eGo ran approximately two to three times as fast as the USB 2.0 drives.

Though eSATA is the fastest interface, two drawbacks inhibit its practical value in portable drives. First, the eSATA connector was not designed to carry power, so you must use an AC adapter to power a drive us­­ing the eSATA interface. Second, eSATA drives aren't reliably hot-pluggable; in order for the drive to show up under Windows Explorer as a drive letter, you must plug the drive in before you boot or you must reboot after attaching it.

FireWire 400 and 800 behave the same way USB 2.0 does, except that they're better. Seconds after you plug a unit in, the drive letter appears; and unlike with USB 2.0, underpowered ports are rare.

Unfortunately, FireWire 800 ports are hard to find except on Macs. Adding one to a Windows PC costs $30 or so for an add-in card and even more for a notebook adapter card. FireWire 800 is backward-compatible with FireWire 400 (with an adapter cable); and thanks to cameras and DVRs, those ports are relatively common. The FireWire drives we tested included a FireWire 400 port or an 800-to-400 adapter cable, so you can probably patch together a FireWire 400 setup without an additional cash outlay.

Power is an important issue with portable drives: eSATA requires a separate AC adapter, and many USB ports on netbooks, laptops, and even PCs are underpowered. No one wants to carry an AC adapter around with them. Of the 22 models we reviewed, 21 relied for power on a single USB 2.0 port on a desktop PC. The sole exception was the WiebeTech ToughTech XE Mini, with its unpowered combination USB 2.0/eSATA port. But even the Wiebe­Tech didn't need an AC adapter when attached via FireWire 400 or 800.

One way to deal with underpowered USB ports is to use a two-to-one USB cable that draws power from two separate USB ports. Iomega's eGo drive, all three Rocstor units, and Seagate's FreeAgent Go docking station shipped with these hedge-your-bet accessories.

Yet another USB drawback that you might run into: USB 2.0 drives attached to PCs sometimes prevent them from clearing POST (power-on self-test) and booting. I've never been able to trace the cause of this phenomenon, but I've experienced it on a number of different PCs.

Capacity

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.

Performance

Drives equipped with an eSATA or Fire­Wire 800 bus were much faster than their USB 2.0 cousins, and eSATA was about 10% 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%. 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.

Rugged Design

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.