How to Buy a Hard Drive

The Big Picture

Today's hard drives have stunning capacities: With the advent of perpendicular magnetic recording, 1 terabyte (1TB) is the current maximum capacity for a single drive. As always, the drive you buy today will give you more storage capacity for less money than the one you could have bought a year ago.

This increased storage capacity has made it economical to turn your PC into a high-powered multimedia machine with plenty of room for accommodating all of your digital photos, a raft of digital music files, and the video files from your digital camcorder or from a TV tuner card. A single 1TB hard drive can store nearly 120 double-layered DVDs' worth of video.

Innie or Outtie?

When shopping for a hard drive, you must first decide whether to go internal or external. An internal drive is a bare drive that goes inside your PC, attaching directly to the motherboard or interface card via PATA or SATA (SATA is the newer standard supported by current PCs). An external, direct-attached drive uses the same basic mechanism, but it's housed in an enclosure that connects to your PC via the USB 2.0, FireWire, or eSATA bus. Another option is an external network-attached storage (NAS) device that connects to your router via ethernet.

Internal drives are suitable for replacing or expanding the storage of a single PC. You can either replace your system's primary C: drive or introduce additional drives to your system, depending on how many drive bays your PC has free (most PCs have at least one spare internal drive bay). Standard drives spin at 7200 rotations per minute and come with capacities of up to 1TB; high-performance models spin at 10,000 rpm and come with capacities of up to 150GB (15 percent of the storage a 1TB drive offers).

Internal drives commonly appear in two flavors: PATA (Parallel Advanced Technology Attachment), also commonly called IDE drives; and SATA (Serial Advanced Technology Attachment). All other things being equal--and prices generally are--you should opt for SATA, the newer of the two interfaces, if your PC supports that connection. SATA drives don't require you to configure jumpers as PATA drives do; their thinner cables restrict the flow of air inside your system less than PATA cables do, and they are easier to connect. SATA drives are sometimes slightly faster than PATA drives, but the performance tends to be nearly identical; you won't see a dramatic performance difference unless you combine drives in a RAID (Redundant Array of Independent Disks) setup. Still, you can be assured that the motherboard of any PC you purchase in the foreseeable future will support SATA drives, whereas they may not support PATA drives as time goes on.

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 ranking internal hard drives and external hard drives, and network-attached storage devices.