Choosing a Hard Drive

What, Exactly, is a Hard Drive?

A hard drive is a stack of magnetic disks that spin at very high rates of speed (7200 RPM for a modern EIDE or SATA drive, and 10,000 RPM for a SCSI drive) and are used to store your computer's data.

Unlike RAM, the hard drive is a semi-permanent storage device. It is non-volatile. That means it continues to hold data even when power to the drive is turned off (or even if the drive were removed from the computer, for that matter). A properly functioning hard drive will retain data until the user or a program instructs it to delete or modify that data.

The disks are enclosed in a protective casing that also contains the drive motor, servos, actuator arms, read/write heads, and the logic circuitry necessary to interface with the system and read from and write to the magnetic disks. Hard drives also contain their own ROM, RAM cache, and controller circuitry.

Types of Hard Drives

There are several different types of hard drives available for desktop computers, distinguished mainly by the interface, or type of connection, between the drive and the computer.

Very high-end computers often use SCSI (pronounced "skuzzy" and standing for "Small Computer Simplified Interface") drives, which are capable of higher data transfer rates. But for most home computer users, SCSI drives are prohibitively expensive. They also require special controllers and are a bit complicated for most beginners to configure.
Until recently, most home and small office computers used EIDE (Enhanced Integrated Drive Electronics) drives, which were commonly known as ATA (short for ATAPI) drives. Nowadays they're called PATA (Parallel ATA) drives, to distinguish them from SATA (Serial ATA) drives. The designation ATA is followed by a number (33, 66, 100, or 133) that gives the drive's maximum data transfer rate in MB/second. ATA-33 and ATA-66 hard drives are now obsolete. ATA-100 and ATA-133 are still available, but are rapidly being replaced by SATA drives.
Almost all new desktop and laptop computers use Serial ATA (SATA) drives. SATA replaced the EIDE hardware interface while maintaining the ATA command set, enabling much faster data transfer rates than EIDE drives, but with fewer compatibility and configuration issues than SCSI drives. SATA drives also are less expensive than SCSI drives of comparable capacity.

How Big a Hard Drive do I Need?

Well, that depends.

Hard drives with capacities in excess of a Terabyte are now available. But a 250 GB drive is probably plenty for a single user who mainly uses standard office applications and doesn't store a lot of graphic, video, or music files. Chances are that the drive will wear out before you fill it up.

But 250 GB drives are considered pretty small as hard drives come these days, so you'll probably find that you can buy a much larger drive for about the same price.

If you're into digital photography, music, or video, then you'll want a much bigger drive for your homebuilt computer -- probably something in the 500 GB to 1 TB range. The same holds true for a computer that will be used by multiple users.

It's a lot easier and more economical to install a larger drive to begin with, then to have to install a larger drive later on when you have run out of drive space. So when pondering whether it's worth an extra ten bucks to step up to that bigger drive, the answer is probably yes.

There are many companies that make hard drives, but I happen to like Seagate, Samsung, and Western Digital.

Understanding the Importance of Hard Drive Cache

The hard drive cache (or buffer) is a little bit of DRAM on the hard drive's logic board that stores frequently-requested data so it doesn't have to be repeatedly read from the drive. This speeds things up a lot, and a larger cache can dramatically improve hard drive performance and computer speed.

The amount of hard drive cache at the time of this writing ranges from 2 MB on el-cheapo drives, to 64 MB on extremely high-end drives. Personally, I suggest you don't use a drive with less than 16 MB cache. Not only does more cache improve the computer's performance, but drives that come with a larger cache tend to be better-built, higher-end drives with longer warranties.

One way to save a little money is to look for a drive with a lot of cache, but which is of a size that the manufacturer is discontinuing. As drives in excess of a Terabyte are now available, many manufacturers are discontinuing production of their smaller drives that are still very high-end in terms of quality. These drives are usually sold at deep discount, but they're still great drives. They're just smaller than what people want these days. But they may be more than big enough for your needs.

So what it boils down to is this: Look around for a high-quality hard drive with a lot of cache, in a size that satisfies your storage needs, but that doesn't break the bank. Don't think you need the biggest drive in the store unless you really, truly, honestly need all of that storage. You'll get better performance from a smaller drive with a larger cache, than from a larger drive with a smaller cache.

Saving Money on a Hard Drive

Most hard drive manufacturers make hard drives in both OEM (Original Equipment Manufacturer) and consumer packaging. The consumer versions typically come in brightly-colored boxes that contain the hard drive, a cable (maybe), the screws, an instruction manual, and a bootable utility that helps partition the drive or copy an existing drive to the new drive. The OEM version typically comes in a plastic bubble that contains the drive itself, maybe the screws, and nothing else.

Many home computer builders prefer the OEM drives because they're usually much less expensive than the comparable consumer-packaged drives. But there are a couple of things to be careful of. Firstly, OEM drives are packaged in bulk cases that provide good shipping protection while they're intact. But once the package is opened a a drive removed, it has a lot less protection than a consumer-packaged drive. So the likelihood of an OEM drive being damaged in shipping is slightly higher than a drive that's consumer-packaged. Reputable vendors know this and add their own cushioning, however..

Secondly, you probably won't be able to use the warranty on an OEM drive if it should fail. OEM drives are intended for sale to computer manufacturers, and the warranty exchange program works differently for OEMs. Long story short: Unless you're registered with the drive manufacturer as an OEM, the chances are they they will not honor any warranty claim you file on an OEM drive. (The vendor from whom you purchased it may honor the warranty, however. Ask before you buy.)

Remanufactured or Reconditioned Drives

Most manufacturers also sell "remanufactured," "reconditioned," or "factory-repaired" drives. Personally, I don't think the price difference justifies the chance you're taking unless the drive carries the same full warranty as the company's new drives. The way I see it, if the drive manufacturer is telling me the drive's "good as new," but doesn't want to warrant it, something isn't right. If you're on a tight budget I'd say go with a new OEM drive rather than a refurbished one.

Next Page -> ATA Hard Drive Configuration

Getting Started
- Components
  - Hard Drives
    - The Hard Drive (This Page)
    - ATA Drive Configuration
    - ATA Drive Jumper Settings
  - Other Storage Devices