About the only time the average computer user is not concerned with running out of storage space is the first day a PC is in use. Start installing programs, copying over tons of backup archives, and filling folders with photos, music, and videos, and all those initially voluminous gigabytes can melt away before your eyes. It may take a month, it may take a year, or it may take two, but no matter how much free storage you start out with, you're eventually going to need more. Remember the old axiom: Data always expands to fill available space.
An internal hard drive would seem like an easy thing to buy: Just find the biggest one you can afford, and you're all set. Go shopping, however, and you'll rapidly discover just how overwhelming the process can be. Are multiple terabytes (TB) of storage space worth paying for? How fast a rotational speed is best? And is one drive enough? This guide will help you wade through these and other questions that are standing in the way of the storage space you probably want and almost certainly need.
Remember, these guidelines are only for internal hard drives—the kind you'd use for permanently housing your operating system, programs, and data. If you're looking for an external drive, for extra-secure backup and for carrying around your files with you wherever you go, be sure to read "How to Buy an External Hard Drive." Or, if you're in the market for bleeding-edge and blazing-fast storage, "How to Buy a Solid-State Drive" will help you. But stick here and we think you'll find that shopping for stay-in-place hard drives really isn't hard at all.
How Much Space Do You Need?
When you're shopping for an internal hard drive, the most crucial characteristic is its size. This will affect every other choice you make and how much you pay—unsurprisingly, larger drives are usually (but not always) more expensive than drives with smaller capacities. If you regularly shoot videos or use your PC for recording television, go for the biggest hard drive you can get: upwards of 1TB, maybe even upwards of 2TB. Serious photographers who store lots of photos in RAW format will also want a fair amount of space, as will music lovers with vast MP3 or AAC libraries and serious gamers. (If all you play are casual games, you're probably fine.) Everyone else can probably get away with less; you don't need much space to just install Windows 7 and
Note: Although current hard drives offer capacities up to 4TB, some PC systems (particularly older ones, or those still running Windows XP) may have trouble recognizing all the space on drives larger than about 2.19TB. A number of companies have developed workarounds for this: Western Digital includes a hardware-based host bus adapter (HBA) with drives like its 3TB Caviar Green, and motherboard manufacturer Asus and storage magnate Seagate have developed software applications that provide access to all that space under certain conditions. Just be prepared to do a (tiny) bit of extra work if you're desperate to own the biggest drives on the market. (For more insight into this issue, read "The Problem with Big Hard Drives.")
How Many Drives Should You Buy?
Though mainstream systems with only one hard drive are still the most common configuration you'll find, many manufacturers and power users have begun switching over to multiple-drive systems. There are some real-world benefits to having more than one drive installed on your computer. Chief among them are speed and value, which we'll get to later, and the security of knowing that neither a catastrophic Windows crash nor a freak power supply failure will wipe out a decade's worth of cherished memories or vital business records. Having one drive exclusively for your programs and at least one drive for everything else is about the best compromise possible. If you don't think you'll need all that space, a single, high-quality drive will be fine.
Interface
The method by which the drive connects to the computer can have a drastic impact on its performance. Almost every consumer drive you'll see these days uses Serial ATA (aka SATA), in either the older 3Gbps or the newer 6Gbps speed. If your computer's motherboard has a 6Gbps (SATA III) port, and the drive supports the technology, definitely use it—it operates at twice the speed of the last generation of SATA. If you've had your PC really a long time, there's a chance it may still use a Parallel ATA (PATA, also known as IDE) port, which is wider and slower than SATA. Though you can still find a few PATA drives floating around out there, you're better off using the speedier, more-convenient SATA if at all possible. Other interface technologies, such as Serial Attached SCSI (SAS) rarely show up in consumer systems, so you probably won't need to worry about them.
Form Factor
Most desktop hard drives come in the 3.5-inch form factor, which lets them fit easily into the bays and caddies used in most PC cases. But some newer drives use a still-tinier 2.5-inch form factor. The physical size of a drive doesn't indicate its performance—one of the fastest hard drives out there, the WD VelociRaptor, is a 2.5-inch drive in a 3.5-inch frame—but it can cause problems at installation time. Not all cases have easy ways to mount 2.5-inch drives, and many of the ones that do require using trays or special brackets that fit in the 3.5-inch drive bays. Before buying a 2.5-inch drive, make sure you know how easily your computer will be able to accommodate it.
RAID
If you've got more than one hard drive in your system, there's nothing wrong with just letting each one operate independently. But setting them up in a RAID configuration can give you added options, performance, and security. With RAID, which stands for Redundant Array of Independent Disks (or Inexpensive Disks), you can "combine" multiple smaller drives to create one big drive (RAID Level 0, or "striping"), a single "mirrored" drive that offers no added space but guards against data loss (RAID Level 1), or a number of other configurations. Many motherboards today have integrated RAID controllers; check your system or motherboard manual if you're not sure yours does. RAID is too hefty a subject to cover in depth here; if you'd like to learn more, check out our story, "RAID Levels Explained."
Our Recommendation
The drive or drives you choose will depend primarily on your specific computing lifestyle and the amount of money you have to spend. But our personal preference is to buy a modestly sized but fast main drive, such as a 10,000rpm VelociRaptor or an SSD, and install all your programs on that; and keep a second, bigger hard drive on hand for our data, even if it spins at slower speeds. (This is where those "green" drives come in especially handy.) Be sure to choose 6Gbps SATA drives for both uses if your computer supports the technology.