How to Buy a Hard Drive

Detachable external drives are more versatile than internal drives: They let you add storage capacity to a PC whose internal drive bays or connections are maxed out. And you can share an external drive among multiple PCs and store it in a safe place when using it as backup media.

Network-attached storage (NAS) devices allow easy access from any PC attached to your network and can be placed in a relatively safe location. Some multiple-drive, high-capacity NAS devices offer perks such as printer and Internet file access so you can share printers across the network or access files from anywhere on the Web. NAS's biggest drawback is that you need to transfer data via ethernet, typically using the TCP/IP protocol, which generally makes NAS the slowest option.

In the end, hard drives are all about capacity or they're all about speed--depending on your needs. Our tests show that all of today's hard drives perform adequately when running regular business applications. Nevertheless, capacious, speedy drives particularly benefit people who process large files, images, and digital video.

Alas, the fastest, largest-capacity hard drives carry a price premium. But you'll probably be able to find this month's high-capacity model at a much more affordable price in the not-too-distant future. By contrast, high-performance drives tend to stay more expensive for longer--until their next capacity bump-up comes along.

For performance evaluations, peruse our Top 5 charts rankinginternal hard drivesandexternal hard drives, andnetwork-attached storage devices.

Key Features

Even the relatively inexpensive PCs on ourTop 10 Value Business Desktop PCschart typically come with hard drives of at least 250GB, which is far more space than you'll need for an operating system, applications, and several years' worth of e-mail messages and typical documents. Capacity matters most to people who archive or edit digital photos, digital audio, or digital video. Video in particular can be a space hog: For example, the contents of a 1-hour MiniDV camcorder tape consume 13GB.

If you want high capacity inside your desktop, remember that you don't have to get it all in a single package: Most PCs have room for at least two internal hard drives (including your primary drive), and a typical big tower can accept even more. You'll usually save money by purchasing two 500GB drives instead of a single 1TB model at a premium. But keep an eye out for rebates and advertised specials; for example, with promotions, you may be able to find a 1TB model for the same price as two 500GB models. And of course, make sure that you have available interface ports; if not, you may have to purchase an add-in card.

External direct-attached drives come in capacities of up to 1TB for single-drive models, some manufacturers achieve the same total capacity with two 500GB drives or four 250GB drives striped together in a RAID 0 or disk-spanning configuration. Portable external drives, which use a notebook-size 2.5-inch or 1.8-inch hard disk, currently max out at 250GB. Affordable, single-drive NAS boxes range from 160GB to 1TB, while more-sophisticated multiple-drive units can be configured in various ways for capacities of up to 3TB and/or for improved speed. It's wise to go for as much capacity as you can afford--especially for a shared network drive, since multiple users are likely to fill it relatively quickly.

High-end desktops and multiple-drive NAS boxes often use RAID configurations. Your motherboard or add-in drive controller must support RAID in order to use this feature.

RAID 0, the most common setup, delivers faster performance by splitting or striping data across multiple drives. Its drawback is that if one drive fails, the data on all drives is lost--so you'll need to keep your backups current.

For systems that need to minimize down time, RAID 1--in which data is written redundantly or mirrored across multiple drives--is a popular alternative. If a drive goes bad, the system can continue to run on a good one until you have the opportunity to install a new drive and rebuild the array. The drawback to this approach is that the usable capacity is only as large as the smallest drive being used--two 250GB drive paired in RAID 1 provide 250GB of storage, not 500GB, and a 250GB drive paired with a 200GB drive yields only 200GB of mirrored storage.