Über die Autorin bzw. den Autor

David Groth is a full-time author and consultant. He is the author of the Sybex's bestselling Network+ Study Guide as well as I-Net+ Study Guide and Cabling: The Complete Guide to Network Wiring. Groth holds many technical certifications, including A+, Network+, Server+, Security+, MCSE, and CNI.

Ron Gilster (CCNA, CCSE, i-Net+, Network+, A+, MBA, and AAGG) has been involved with Cisco networking and internetworking since 1993 as a trainer, teacher, developer, merchant, and end user. He has more than 35 years of total computing experience, including more than 15 years involved with the networking of computers. He also has extensive experience consulting in computer-related areas, including working on mainframes, minicomputers, and virtually every type of personal computer and operating system that exists. He has held consulting and management positions with several high profile companies. Ron is semi-retired, writing and teaching the occasional college course. He is the author of CCDA For Dummies, Cisco Networking For Dummies, A+ Certification For Dummies, Network+ Certification For Dummies, Server+ Certification For Dummies, and i-Net+ Certification For Dummies, plus several books on networking, including wireless networking, the Internet, computer hardware, computer and information literacy, and programming.

Megan Miller is an editor and writer with 20 years experience in publishing, technical project management, and interactive communications.

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Wiley Pathways PC Hardware Essentials

John Wiley & Sons

Chapter One

Starting Point

Go to www.wiley.com/college/groth to assess your knowledge of hard drives.

Determine where you need to concentrate your effort.

What You'll Learn in This Chapter

* The components and characteristics of hard drives and how they work

* PATA and SATA standards for hard drives and how to install and configure an ATA hard drive

* SCSI standards for hard drives and how to install a SCSI hard drive

* Hard drive partitioning, formatting, and management

After Studying This Chapter, You'll Be Able To

* Compare hard drives in terms of industry standard ratings

* Identify recent hard drive standards

* Distinguish unique installation considerations for different hard drive technologies

* Choose an appropriate hard drive and interface for an existing PC Determine partitioning and formatting limits and options for a given operating system

* Install, partition, and format a hard drive

* Use system utilities to review the status of a hard drive

* Troubleshoot a faulty hard drive

INTRODUCTION

The system memory that is used by the PC to temporarily store data coming from and going to the CPU is often referred to as primary storage. In addition to system memory, PCs also need permanent, nonvolatile storage areas for larger amounts of data. Nonvolatile means that the data stored on a component is not lost when power to the component is turned off. These nonvolatile storage components are often referred to as secondary storage. Today, the most common secondary storage components are hard drives, and these typically store the bulk of the data that a PC uses. This data includes not just user documents and files, but also user and system software, such as Microsoft Word and Microsoft Office, and any files and data needed to support running these applications. Hard drives typically reside inside the computer (although there are external and removable hard drives) and can hold more information than other forms of storage.

7.1 Understanding How Hard Drives Work

One of the most common upgrades to a PC is adding or replacing a hard drive in order to gain more storage space. To choose a compatible drive for your system, it is important to understand a few of the basics of hard drives and how they work. Understanding the main characteristics of hard drives and how hard drives are rated will also help you compare equivalent hard drives from different manufacturers and select the one that is right for your needs.

7.1.1 Hard Drive Components

Hard drives, also called hard disk drives, hard disks, or fixed disks, consist of several small, identical disks called platters stacked together and placed in a sealed enclosure to protect them from dust or damage. The platters are made of aluminum or glass, and are coated with a thin layer of magnetic media that stores the actual data.

The platters are mounted through their centers on a small rod called a spindle. The disks are rotated about the spindle at a speed typically between 4,500 and 15,000 revolutions per minute (RPM). As they rotate, read/write heads float approximately 10 micro inches (about one-tenth the width of a human hair) above the disk surfaces and make, modify, or sense changes in the magnetic positions of the coatings on the disks. Read/write heads have sensors and magnets used for reading and writing magnetic charges on the platters' surfaces. The read/write heads are connected to an actuator arm, which is used to precisely position the heads over the correct area on the platters (Figure 7-1).

Hard drives also contain a logic board that contains the circuits and chips that control the drive's performance. The disk controller is the main circuit on the logic board that controls everything from handling requests for data to managing the mechanics of the motor, actuator arm, and read/write heads.

Also essential to the functioning of a hard drive is the host adapter, or host bus adapter (HBA), logical circuitry that physically connects the hard drive to the "host"-the PC. The host adapter handles basic input/output processing, converting signals from the hard drive controller to signals the PC can understand. The host adapter may be an expansion card plugged into the motherboard or its circuitry may be built directly into the motherboard.

Hard drives come in several sizes. Older hard drives were designed to fit 5.25 inch drive bays but most modern desktop computer hard drives today are designed to fit in the standard 3.5 inch drive bays. Older hard drives were much taller than modern drives and are called "full-height." Modern drives are shorter, "half-height" or even slimmer. Inside the PC, internal hard drives are connected by cables to the power supply and to the host adapter.

7.1.2 Drive Geometry

To read and write data to the magnetic platters of a hard drive, the drive is electronically organized into sections recognized by systems software. This organization is called drive geometry. The components of a hard drive's physical geometry include:

* Heads: A hard drive usually has one read/write head for each surface of a platter; a drive with four platters has eight read/write heads.

* Tracks: Data is written to and read from the surfaces in concentric rings called tracks. The rings, or tracks, are numbered from the outside track in, with the outside track given the initial number 0. The total number of tracks that a surface can have depends on the drive's engineering; today's hard drives may have over 16,000 tracks on each surface.

* Cylinders: Because all heads are on a single actuator arm, the heads read the same track number on each surface at the same time. If the actuator arm moves to Track 12, all heads will be reading from Track 12 on the separate surfaces. The collection of tracks at a single actuator-arm position is known as a cylinder (Figure 7-2). The total number of tracks per surface is the same as the number of cylinders. In fact, the disks' tracks aren't treated as individual tracks on single disks; they're treated as cylinders, and manufacturers more commonly note the number of cylinders that a drive has. If you need to know the number of total tracks a hard drive has over all surfaces, you can multiply the number of heads by the number of cylinders.

* Sectors: To organize and locate separate chunks of data on a surface, the platter is divided into 60 or more wedges that divide short sections of tracks into smaller segments called sectors. Sectors are the smallest accessible portion of data on a track, and all sectors, regardless of their physical size, are defined as holding 512 bytes of data. When information is read from or written to a drive, the heads read or write a sector-sized division of a cylinder, from top surfaces to the bottom. In this physical geometry, with sectors defined by wedges, a certain amount of waste is built in: The sectors at the outer edges are physically quite a bit larger than inner sectors. To fit more sectors in to the outer tracks, zone bit recording (ZBR), or multiple zone recording was built in (Figure 7-3). ZBR divides the platters into different zones, nearer and further away...