How to Buy a Hard Drive
Your PC's internal hard drive is a real workhorse--the most critical component of your system after the CPU and memory. The hard drive is the hub where your operating system, programs, and data are permanently stored and accessed.WD-elements-500GB.jpg
If you edit movies, take lots of digital photos, play games, or listen to music files on your PC, a big, fast internal Parallel or Serial ATA hard drive can dramatically improve your overall computing experience. If you need more storage or a means to back up your PC's internal drives, you can add an external hard drive--available in USB 2.0, FireWire 400 or 800, or external SATA flavors. And if you want centralized storage, consider buying a network-attached storage device. NAS devices are continually improving, and can be a convenient way to add storage that all of the PCs on your small or home network can share.
To enjoy multimedia on your PC, you need a spacious hard drive. Here's how to shop like a pro for an internal or external drive.
Key Features
Don't know capacity from rotational speed, or IDE from SATA? We define the terms you're likely to see when shopping for a hard drive, and we tell you which specs are the most important ones to consider.
Key Features
Important: Capacity
Even the relatively inexpensive PCs on our Top 10 Value Business Desktop PCs chart 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.
Somewhat Important: RAID Setup
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

Typically, dual-drive RAID boxes offer the choice of RAID 0 or RAID 1. Multiple-drive direct-attached or network-attached boxes--some enclosures support up to five drive bays--generally complement those basic RAID levels with RAID 5 (parity--offering your best bet for data redundancy) or RAID 0+ 1. You can also set up a RAID for your internal drives; however, your motherboard or add-in drive controller must support RAID.
Important: Rotational Speed
All 3.5-inch, desktop-size internal SATA hard drives--as well as most current PATA drives--spin their disks at 7200 rpm. A handful of drives spin at 10,000 rpm; they are aimed at enthusiasts and enterprise users. Typically, the faster the disks spin, the faster the data is read and written--but the average buyer won't want to pay a price premium for a 10,000-rpm model.
Portable external drives have the biggest range in rotational speeds. Models are currently available in 4200-rpm, 5400-rpm, and 7200-rpm flavors. The most common of these is 5400 rpm. You'll see a difference in transfer speeds if you copy a lot of data--say, photos from a full 2GB memory card--to your hard drive, so keep a close eye on these specs, and beware of vendors that don't identify the drive's rotational speed.
Somewhat Important: Seek Speed
Average seek speed, measured in milliseconds, refers to how fast, on average, drives can find a particular piece of data. This is a minor consideration: For most people, the effect of differences on this measure in everyday use is negligible. The exception is when a drive is called upon to assemble many small pieces of data scattered in different areas of the hard drive, such as when copying large folders full of many small files. Jumbo drives tend to have somewhat longer seek times.
Important: Interface
Nearly all internal drives in new PCs use the SATA interface, which supports maximum transfer rates of either 150MB or 300MB per second. The drives with a 300MB-per-second maximum transfer rate cannot take advantage of their wider bandwidth in typical desktop use, though they shine in RAID combinations.
PATA drives, which support maximum transfer rates of either 100MB per second or 133MB per second, are still widely available. There's little advantage to one or the other; hard drives never sustain data-transfer rates approaching either maximum, though drives can sometimes push out of data at rates approaching the high-end speeds for brief bursts.
Both PATA and SATA interfaces are backward-compatible: For example, you can run an older ATA-33 drive on an ATA-133 bus or a 150MB-per-second SATA drive on a 300MB-per-second bus. But although PATA-to-SATA adapters are available, you should match a PATA drive to a PATA interface whenever possible, to get the best performance from it. SATA drives work with the SATA interface only. Inexpensive PCI Express and PCI add-in cards are available that let you add a SATA interface to a computer that lacks it; PATA and PATA/SATA models are available only for PCI.
Most external drives have a USB 2.0 interface or a dual USB/FireWire interface. Other interface configurations are dual USB2.0/FireWire 400; FireWire 800; and eSATA. USB 2.0 and FireWire 400 perform slightly slower than a comparable internal drive, but either is more than acceptable for auxiliary storage or backup. (A USB 2.0 drive will work with a USB 1.1 port, but its performance slows to an unacceptable level.) wd Passport Essential SE portable hdd 1TB

FireWire 800 is quite fast, but this interface is relatively rare on desktop PCs. For high-performance external storage, go with an eSATA direct-attached drive. These drives are becoming increasingly popular; and while they don't offer the universal connectivity of a USB 2.0-enabled drive, they're as fast as an internal drive--and sometimes they include a USB connection, for good measure.

To install an eSATA drive, you'll need an open external port: Though eSATA drives come with a pass-through connector that provides an external port, you'll need an open internal SATA port to attach the connector to. If you don't have an open internal port but do have an available PCI slot, an inexpensive PCI add-in card can provide external SATA, USB 2.0, or FireWire ports for systems that lack them. Likewise, you can find PC Card adapters that add USB 2.0 and FireWire ports to a notebook, if your system is so old that it lacks these interfaces. However, FireWire and FireWire 800 use different connectors, so they are not cross-compatible.
abit ethernet connection to hook up to your network. As such, NAS devices are generally pokier than direct-attached external models. Look for NAS devices that provide USB 2.0 ports for accommodating additional hard drives so you can expand capacity or share attached printers across the network.

Somewhat Important: Buffer
When a system requests data, a hard drive will fetch what is requested and load its buffer memory with extra information that the processor is likely to ask for next. Theoretically at least, a larger buffer size should help keep the data flowing better, especially in disk-intensive tasks such as file searching. Most desktop drives--and all of the ones on our Top 5 charts--have buffers of either 8MB or 16MB. Value-priced PATA drives may have 2MB buffers.
Somewhat Important: Noise
If you are building your own PC to use in your living room as a media center hub, noise may be a significant issue. Many hard-drive makers offer versions of their drives designed for use in personal video recorder or media-streaming environments. Look for these specialty drives if you're looking to reduce the noise output by your system.

 Hard-Drive Shopping Tips
If you outgrow your existing storage, it can be easier and cheaper to upgrade a drive than to buy an entirely new PC. When you're ready to start looking, print out these tips for handy reference

Hard-Drive Shopping Tips
Are you ready to take the plunge and buy a big new hard drive for your PC? Here are PC World's recommendations for what you should consider, both before you buy the drive and when you're actually shopping.

Determine whether your PC can take advantage of a new drive. Newer PCs can make best use of a new drive's increased performance and capacity. An old PC with a slow CPU and limited RAM won't be able to fully exploit the performance potential of a new drive. You've probably reached the point of diminishing returns if your PC's interface speed--say, ATA-33--is slower than the interface speed of the cheapest drive available.
If your middle-aged computer is still working acceptably, more storage capacity and speed may be just what the doctor ordered. Installing a new drive as your main drive for running Microsoft Windows and various productivity applications might improve performance appreciably. Older PCs may need both a PCI interface card to get the best drive performance and a vendor-supplied driver or BIOS update to be able to recognize the capacity of large drives; Windows XP's drivers allow use of a drive's full capacity as well.
Make sure your case has space. Most desktop PC cases have at least one, and sometimes several, internal drive bays--places where you can mount extra hard drives. But check your manual or open the case: If you have a smaller, low-profile case, you may not have room for another internal drive, meaning that you may not be able to use the old and new drives simultaneously.

Also, check your power supply to see whether it has a spare plug for an additional internal drive. Another consideration: Will the power supply have enough juice to run an extra drive along with your system's existing components?
Supersize your purchase. It's smart to buy a drive with more capacity than you think you'll need. If you're absolutely sure that you won't be using multimedia-intensive applications that eat up huge amounts of space (such as programs that edit video), or storing digital photos or MP3 audio files, you might not need a maximum-capacity drive. But be sure to anticipate your future needs when deciding on the size of your new drive--especially if you plan to keep your existing PC for a couple more years. Match the drive and interface speed. The ATA-100 and ATA-133 interfaces of current drives are faster than the internal interfaces on many older PCs; check your PC manual or contact your computer vendor to find out for sure. An easy-to-install interface card (about $25) can guarantee that you get maximum performance from your new drive. If you want to add a SATA-300 drive to a system with SATA-150 connectors, however, just do it. The nominally slower interface should not choke the performance of a SATA-300 drive.
Use an external drive for backup. External drives are great for backing up your PC, and many models have one-touch backup buttons that make the process even easier. The fastest external hard drives are the new eSATA models. Make sure that you have at least one free internal SATA port for models that come with a pass-through cable, or buy a model that that offers eSATA ports through a PCI interface.

Use a portable drive with your notebook. External models that use hard drives intended for laptops tend to be optimized for mobile use. One relevant feature is a ruggedized enclosure with a high shock rating, meaning that it can absorb a typical impact from a desk to the floor, for example. Some drives may also have g-force sensors that can detect when a drive is in motion and park the heads to avoid damage to the disk. Typically, though, that feature is found on internal notebook drives, rather than on add-on drives.
Consider a NAS device. They're a great choice for backup as well as for making photos, videos, music, and other files available to everyone on your network. NAS devices connect to your network via ethernet, which means middling performance, but in most cases they also include USB 2.0 ports to share a printer or to expand storage capacity in case you run short in the future. See our Top 5 Networked-Attached Storage Devices for pricing and specs.
Look for bargains. Competition among hard-drive makers is intense, and dealers often run specials that let you pick up a new drive for an amazingly low price. These deals tend to be on smaller-capacity or slower drives, however. Don't expect specials on the largest-capacity drives, since these may be in short supply and usually sell at close to list price until the next generation of drives appears.

Buy a retail kit. Hard-drive kits include mounting hardware, cables, detailed instructions, and (often) software that eases installation. A kit may also include an application for cloning the contents of your old hard drive onto the new one, which then becomes your new main drive. If you buy via mail order, be sure to get the kit. The alternative is a "bare drive," essentially just a drive in a Mylar bag, often without screws, software, or even instructions beyond a technical data sheet. Bare drives are sometimes available online at bargain prices, however, and plenty of online installation help is available
Use add-on software. Power users who purchase a bare drive and aren't running Windows XP may need extra software to ease the process of integrating the new hard drive into their PC. Even if you buy a packaged drive upgrade kit, you might want to use Symantec's Ghost or Acronis's True Image to back up and clone a drive. Symantec's Partition Magic and Acronis's Disk Director let you fine-tune how your new drive stores data.

Final Recommendations
General users: If you typically use your PC for Web surfing, working on Microsoft Word documents, handling e-mail, and perfiorming casual digital imaging, a lower-capacity drive may work for you. Opt for an inexpensive 300GB drive, using whichever interface is convenient for your needs.
Multimedia hounds: If you store a lot of digital images, audio, or video, consider buying a single 750GB or 1TB drive. If you also edit images and video, go for internal or external models on our Top 5 hard-drive charts that show the best test results on related imaging tasks; an eSATA drive will give you the best performance.

Gamers: A popular choice for performance-hungry gamers is a RAID 0 rig with two Western Digital 10,000-rpm WD Raptor drives. This kicks up your performance but limits capacity, since the WD Raptor is available only in 36GB, 74GB, and 150GB sizes.

Shared storage: If you want a NAS device, get one with the largest capacity you can find--gigabytes go fast when several people are backing up their own digital photo and MP3 collections. Also, aim for one that's easy to upgrade, in case you need to swap out a drive down the road

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How to Buy a Hard Drive