External hard Drives

External hard drives enable you to add storage to your desktop or laptop without having to open the case. Here are details on the types of external drives and the specs you need to know before you shop.

FORM FACTOR

External hard drives come in many shapes and sizes, and most can also be rested vertically to save space on your desk. Some external models are small enough to fit inside your shirt pocket, but these tend to be more expensive on a per-gigabyte basis and offer less storage than more conventionally sized "desktop" external drives. Still, sheer portability makes them a great choice for shuttling data between home and the office.

POWER SOURCE

Laptop users who are constantly on the road and don't require massive storage space should invest in a bus-powered external drive. Bus-powered drives, typically compact, draw power from your computer's USB or FireWire port. Because your laptop provides the juice, these drives eliminate the need to carry a power adapter, although they do eat up battery life. Some bus-powered drives also bundle an external power adapter that you can use when a wall socket is available. Be aware that many portable USB drives require the use of two USB ports—one to deliver data, the other for power.

CAPACITY

In light of the ever-expanding appetite for large multimedia files, you should buy the largest drive you can afford. Even pocket-size drives should provide at least 80GB of storage, and you can get externals with capacities as large as 1.5TB. You do pay a price for mobility and ease of installation, however, as external drives tend to cost more than internal drives of the same capacity.

CONNECTIVITY

Typically, external drives connect to your computer via USB 2.0 or FireWire ports. FireWire now comes in two flavors—400 and 800—that correspond to their maximum data-transfer rates: 400Mbps and 800Mbps, respectively. Some drives have both USB and FireWire 400 ports (these drives are often called "dual interface"), and others support all three connections ("triple interface"). An increasing number of drives feature the speedy external Serial ATA (eSATA) interface, with a maximum transfer rate that can outpace even FireWire 800’s. External SATA drives usually require that you install a PCI card (sometimes bundled with the drive) in your desktop computer or an ExpressCard in your notebook computer in order to connect the drive, however.

NETWORKING

If you have a home network, you can opt for a network-attached-storage (NAS) drive. NAS drives provide an easy way to add storage that multiple computers can share. Some are as basic as a hard drive with an Ethernet port or built-in Wi-Fi; others provide extra USB and FireWire ports that allow you to daisy-chain additional drives to boost your overall network storage space. If a NAS drive has print-server capabilities, you can plug a printer into its USB port and send print jobs wirelessly from any computer on your network.

SPEED

The speed at which a hard drive spins, measured in revolutions per minute (rpm), is directly related to how fast it can retrieve data. Though many current external drives spin at 5,400rpm, a drive with a spindle speed of 7,200rpm is a better choice.

BUFFER

Drives temporarily store data in a memory buffer (or cache) because the device can read from the buffer faster than the drive's platter. A larger buffer can noticeably enhance drive performance. Look for a drive with an 8MB or 16MB buffer, rather than a 2MB buffer.

SOFTWARE

Many drives come with backup and recovery software to ease the archiving of files on your PC. Check each drive's software bundle for the best drive/software combo to suit your personal backup needs.

ENCLOSURES

Do-it-yourself types have another option for external storage: buying a hard drive enclosure that can house an internal drive (or drives). Because internal drives are generally cheaper than externals, this solution can save you money—even more so if you already own a disused internal drive. An enclosure that houses multiple drives can offer the ability to use Redundant Array of Inexpensive Disks (RAID) technology. With RAID, you can split data across several drives to enhance performance (RAID Level 0, or "striping"), or duplicate data on multiple drives for security (RAID Level 1, or "mirroring"). For more information, consult our guide on how to build an external hard drive.

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