Understanding Hard Disk Drives

Before we get into installing hard disk drives, let's take a minute to examine how a hard drive works. As you can see in Figure 4.1, a hard drive consists of multiple rigid-metal platters, stacked on a spindle inside a sealed enclosure. The spindle is attached to a motor that spins the platters at very high speeds.

Figure 4.1. The inside of a hard drive looks like this.

Hard disk platters are coated with a special material that enables the storage of information in magnetic patterns. Data is written to and read from the platter by means of an electromagnetic read/write head. Each platter is divided into sectors; each sector contains 512 bytes of data.

Understanding Hard Drive Specs

When you go shopping for a new hard drive, you need to understand the relevant specifications in order to make an informed buying decision and get the right hard drive for your system. This information, typically available somewhere on the drive's packaging tells you how much data the disk can hold, and how fast it can access that data. (Faster is better, of course and also more expensive.)

Of these specs, you'll want to focus your attention on size, speed, and price. Given the low prices of hard drives today, you'll probably want to spend a few extra bucks to get a larger-capacity drive if your system can handle it. If you're using disk-intensive applications (such as PC games or audio/video editing programs), you'll also want to spring for the faster 7,200 RPM models. And, of course, price is always a factor; make sure you make the price/performance compromise that works best for your specific needs.

Capacity

Disk drive size is typically measured in gigabytes (GB). The bigger the drive, the higher the price.

caution

It's actually possible to buy too big a hard drive. If you're running Windows 95 or earlier, your operating system will only support drives up to 32GB in size. If you're running Windows 98, Windows Me, Windows XP, Windows NT, or Windows 2000, you can use drives that exceed the 32GB limit.

Access Time

Access time is the amount of time it takes for the heads to locate a specific piece of data on the hard drive. Manufacturers typically specify the "average access time," because the actual seek time varies depending on the location of the heads and where the next bit of data is stored.

Spin Rate

This spec measures the speed at which the platters spin, in revolutions per minute (RPM). Faster-spinning drives result in faster data transfer rates (discussed next); most drives today spin at either 5,400 RPM or 7,200 RPM. The slower speed is acceptable for traditional office use, but you'll want a faster drive if you're doing a lot of audio or video-related tasks.

Data Transfer Rate

The data transfer rate is the speed at which the system copies data from the hard drive to your computer (and vice versa). This spec is typically measured in terms of a programmed input/output (PIO) or Ultra Direct Memory Access (UDMA) mode. For example, a drive with a peak transfer rate of 100MBps is labeled UDMA 100 (also known as UDMA mode 5). Make sure the PIO or UDMA mode of your new hard drive matches the specs of your system unit although, in most cases, if you get a faster hard drive than your system can handle, it can be configured to run at a slower mode to ensure compatibility.

Drive Interface Type

There are several different interfaces available that control the communication between your hard drive and your PC. The two primary interfaces in use today are

• IDE (Integrated Drive Electronics). This is the most popular hard drive interface currently in use. (Some vendors use the terms ATA for AT attachment or IDE/ATA to describe drives of this type.) IDE drives use 40-pin connectors, and are quite easy to install and configure. Every PC made today can accept IDE drives; in addition, other types of storage devices, such as CD/DVD and Zip drives, also use the IDE interface.

• SCSI (Small Computer System Interface). This is a more expensive, difficult-to-configure interface primarily used in systems designed for high-end audio/video editing.

Most hard drives today use some variation of these two interfaces. The IDE/ATA standard, especially, has inspired a raft of progeny, all promising faster performance than the basic IDE interface. These subsets of IDE include UDMA, UIDE, AT-6, Fast ATA, and Ultra ATA. All of these interfaces utilize the basic IDE-type connector, so compatibility generally isn't a huge problem.

"Mike Sez"

Given the higher expense and more difficult installation associated with SCSI, I recommend you go with an IDE drive which is what we'll focus on for the balance of this chapter.

If you're working with an older PC, you might encounter some additional, now-obsolete interfaces, such as ST-506, ESDI, and MCA-IDE. If your system uses any of these interfaces, it's an antique; junk the thing and buy a new PC!

Disk Drive Manufacturers

When you're looking for a new hard disk, it pays to stick to the major manufacturers. Here are some of the companies that specialize in magnetic storage media:

• LaCie (www.lacie.com)

• Maxtor (www.maxtor.com)

• Western Digital (www.westerndigital.com)