What to look for in an external hard drive

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Hot-swappable drive bay enclosures: Several companies, including FirmTek, Granite Digital, and WiebeTech, sell hot-swappable FireWire, USB 2.0, and/or eSATA hard drive assemblies. You get a single case, power supply, and cable, to which you add one or more hard drives, each in a special carrier. You can pop out one drive and pop in another quickly, making it easy to rotate backups. But you pay quite a premium for that small convenience.

Multi-drive enclosures: Another recent trend is enclosures containing two or more non-removable drive mechanisms configured as a RAID in order to appear as a single, larger volume. Examples are Maxtor’s OneTouch III, Turbo Edition and LaCie’s Hard Disk MAX.

Pocket-sized hard drives: If you need to back up large amounts of data while traveling, or if your laptop lacks a CD or DVD burner, consider a pocket-sized hard drive. These drives typically use the same 2.5-inch mechanisms that laptops do, and can often be powered through the FireWire or USB cable, eliminating the need to carry a bulky AC adapter with you. (In fact, I like these drives even for backing up desktop computers, because they’re quieter than full-size drives and require less desk space and cable clutter—albeit at a slightly higher price.) Some examples:

  • LaCie Mobile Drives: LaCie makes several lines of pocket-sized hard drives, with various interface options and capacities up to 1TB (in some cases using two drives in one enclosure).
  • Maxtor OneTouch 4 Mini: Maxtor’s pocket-sized drives hold up to 500GB and use USB 2.0 interfaces.
  • OWC Mercury On-the-Go: These drives are available with several different combinations of USB 2.0, FireWire 400, and FireWire 800 interfaces, in capacities up to 500GB (with larger sizes expected soon). You can also buy an empty enclosure and add your own 2.5-inch drive, such as the new Western Digital Scorpio Blue 1TB drive. (The OWC Mercury cases are among the few that can accommodate the Scorpio Blue’s 12.5 mm height.)
  • Seagate FreeAgent Go: Similar to the other drives listed here, these come in capacities up to 500GB (with rumors of a 640GB model in the works) and include FireWire 800, FireWire 400, and USB 2.0 interfaces.
  • Western Digital My Passport Essential SE: This tiny drive with a big name comes in 750GB and 1TB capacities, but has only a USB 2.0 interface.

Encrypted hard drives: When you put a bootable duplicate on an external hard drive, you can’t use your backup software’s encryption feature; if the files have to be decrypted by software before the system can read them, you won’t be able to boot from that drive. And thus, ordinarily, only standard copies and versioned backups can be encrypted—though some programs you might want to use for versioned backups (think: Time Machine) don’t offer encryption as an option. This isn’t much of a worry unless, as I recommend, you store one of your backup drives off-site at all times—if someone else gets their hands on it, they have immediate access to all your data.

One way to get encrypted duplicates, or encrypted versioned backups when using a program like Time Machine, is to use a drive that features hardware encryption. Everything written to such a drive is encrypted automatically, and everything read from the drive is decrypted automatically, by circuitry in its enclosure; instead of typing in a password, you unlock the data by using a physical electronic key or smart card, swiping your finger on a built-in fingerprint reader, or entering a code on a keypad.

Several manufacturers now make such drives (or enclosures to which you can add your own drive); they come in both full-size (3.5-inch) and pocket-sized (2.5-inch) models, with a variety of interfaces. They’re more expensive than standard drives, but are an excellent investment if you store sensitive personal data. Examples include:

iPods: You can use an iPod as a backup device if it has enough free space—but remember, that will limit the amount of media you can store, and you may also wear it out prematurely, since it wasn’t meant for continuous disk use. (Only older iPods with FireWire interfaces can be used as startup disks for PowerPC-based Macs.) iPods are also more vulnerable to theft, since you’re more likely to carry them around with you—so be sure your backups are encrypted! To use your iPod as an external hard drive, open iTunes, select your iPod in the Devices list on the left, and check the Enable Disk Use checkbox. The iPod touch (and iPhone) do not support this feature without the use of a third-party hack.

Brands and warranties: You’ll usually pay more for a brand name than a generic drive. Is the extra money worth it? Often not. The drive mechanisms themselves come from relatively few manufacturers, all of which are quite reputable—it’s the cases, power supplies, and supporting electronics that vary from vendor to vendor. Look for a 3-year or better warranty, and check out the manufacturer’s Web site to look for signs of life and Mac support. But don’t be afraid of second-tier brands.

Warning: Some Western Digital My Book and Passport hard drive models can’t be used to boot a PowerPC-based Mac, even if connected via FireWire. The problem doesn’t affect Intel-based Macs. Go to Western Digital’s site for a full list of affected products.

Joe’s hardware recommendations

Don’t make decisions about hardware based on price alone. You may find the cost of a stack of DVD-R discs, for example, to be a fraction of what a hard drive costs—but that’s only part of the story. Speed, convenience, flexibility, and the ability to make bootable backups all add tremendous value to hard drives. Even if you can afford only one external hard drive, making it part of your backup system will pay for itself many times over in saved time and aggravation. If your budget permits, two or even three moderately large external hard drives are a good way to go.

Network backups are even more convenient (especially if you use a laptop with a wireless network), though they lose a few points for speed. Another advantage: if you’re sensitive to noise, having one less whirring gadget on your desk is a good thing.

If you’re looking purely for the most economical hardware path, use your built-in SuperDrive and record backups onto DVD-RW media. Your hardware cost is zero, and $50 should buy you enough blank media to last years.

Finally, don’t overlook Internet backups. If the volume of files you need to back up is reasonably small and your Internet connection is fast, Internet backup services could be a good supplement or even a substitute for conventional versioned backups. An excellent approach that gives you the best of both worlds without costing a fortune is to use a single hard drive for local duplicates and versioned backups, and then use an Internet backup service (perhaps only for your most essential files) to provide both redundancy and off-site storage for your versioned backups—without requiring you to move any hardware around.

[Joe Kissell has written many books about the Macintosh, including many popular Take Control ebooks. He’s also Senior Editor of TidBits and contributes frequently to Macworld. Take Control of Mac OS X Backups, Fourth Edition was released in September 2009 by TidBits Publishing, and it is completely up-to-date for Mac OS X 10.6 Snow Leopard.]

This story, "What to look for in an external hard drive" was originally published by Book Excerpt.

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