Chapter 11 HARDRIVE TECHNOLOGY

Seite 1

In this chapter, you will learn

how to

■ Explain how hard drives work

■ Identify and explain the PATA

and SATA hard drive interfaces

■ Identify and explain the SCSI

hard drive interfaces

■ Describe how to protect data

with RAID

■ Install hard drives

■ Configure CMOS and install

drivers

■ Troubleshoot hardrive installation

Of all the hardware on a PC, none gets more attention—or gives more

anguish—than the hard drive. Hard drives come in two major types::: The most common type has moving

parts;

the newer and more expensive technology has no moving parts. Let’s

look at both.

Platter-Based Hard Drives:

A traditional hard disk drive (HDD) is composed of

individual disks, or platters, with read/write heads

on actuator arms controlled by a servo motor—all

contained in a sealed case that prevents contamination

by outside air

Moving the Arms The read/write heads move across the platter on the ends of actuator arms

or head actuators.

In the entire history of hard drives, manufacturers have used only two technologies to move the arms: stepper motor and voice coil.

Hard drives first used stepper motor technology, but today they’ve all

moved to voice coil.

Geometry also determines where a hard drive stores data.

We describe the geometry for a particular

hard drive with a set of numbers representing three values: heads, cylinders,

and sectors per track.

Heads The number of heads for a specific hard drive describes,

rather logically, the number of read/write heads used by the drive

to store data. Every platter requires two heads. If a hard drive has

four platters, for example, it needs eight heads.

Cylinders Spindle (or Rotational) Speed

Hard drives run at a set spindle speed, measured in revolutions

per minute (RPM).

Older drives ran at a speed of 3600

RPM, but new drives are hitting 15,000 RPM. The faster

the spindle speed, the faster the controller can store and

retrieve data. Here are the common speeds: 5400, 7200,

10,000 and 15,000 RPM.

Solid-State Drives

Booting up a computer takes time in part because a traditional hard drive

needs to first spin up before the read/write heads can retrieve data off the

drive and load it into RAM. All of the moving metal parts of a platter-based

drive use a lot of power, create a lot of heat, take up space,

wear down over time, and take a lot of nanoseconds to get things

done..............A solid-state drive (SSD) addresses all of these issues nicely.

solid-state technology and devices are based

on the combination of semiconductors, transistors, and bubble

memory used to create electrical components with no moving parts.

That’s a mouthful! Here’s the translation

In simple terms, SSDs (see Figure 11.7) use memory chips to

store data instead of all those pesky metal spinning parts used in

platter-based hard drives.

Solid-state devices use current flow and negative/positive electron

charges to achieve their magic

Solid-state technology is commonly used in desktop and laptop

hard drives, memory cards, cameras, USB thumb drives, and other

handheld devices.

SSD form factors are typically 1.8-inch, 2.5-inch, or 3.5-inch

SSDs are more expensive than traditional HDDs

IDE

The term IDE (integrated drive

electronics) refers to any hard

drive with a built-in controller

Parallel and Serial ATA . Starting around 1990,

an interface called advanced technology attachment (ATA) appeared that

now virtually monopolizes the hard drive market. ATA hard drives are

often referred to as integrated drive electronics (IDE) drives

ATA drives come in two basic flavors:::::::::

The older parallel ATA (PATA)

drives send data in parallel, on a 40- or 80-wire data cable. PATA drives dominated

the industry for more than a decade

but have been mostly replaced

by serial ATA (SATA) drives that send data in serial, using only one wire for

data transfers

American

National Standards Institute (ANSI)

The first ATA drives connected to the computer

with a 40-pin ribbon cable that plugged

into the drive and into a hard drive controller.

The cable has a colored stripe down one side

that denotes pin 1 and should connect to the

drive’s pin 1 and to the controller’s pin 1

The controller is the support circuitry that acts as the

intermediary between the hard drive and the external

data bus.

ATA-2 Many people called these new features Enhanced IDE

(EIDE).

and by

1995, EIDE drives dominated the PC world.

Not Just Hard Drives Anymore: ATAPI ATA-2 added an extension to the ATA specification, called advanced technology

attachment packet interface (ATAPI), that enabled non–hard drive

devices such as CD-ROM drives and tape backups to connect to the PC

via the ATA controllers. ATAPI drives have the same 40-pin interface and

master/slave jumpers as ATA hard drives. Figure 11.15 shows an ATAPI

CD-RW drive attached to a motherboard.

ATA-3 ATA-3 came on quickly after ATA-2

and added one new feature called SelfMonitoring,

Analysis, and Reporting Technology

(S.M.A.R.T.), one of the few PC

acronyms that requires the use of periods

after each letter. S.M.A.R.T. helps predict

when a hard drive is going to fail by

monitoring the hard drive’s mechanical

components

ATA-7

ATA-7 brought the revolutionary was a new

form of ATA called serial ATA (SATA).

Serial ATA FLAT RIBBON SUCKED:::::::::

First, the flat ribbon

cables impede airflow and can be a pain to insert properly. Second, the

cables have a limited length, only 18 inches. Third, you can’t hot-swap PATA

drives. You have to shut down completely

before installing or replacing a drive. Finally,

the technology has simply reached the limits

of what it can do in terms of throughput

eSATA External SATA (eSATA) extends the SATA bus to external devices,

as the name would imply.

External SATA uses shielded cable lengths up to 2 meters outside the PC

and is hot-swappable. The beauty of eSATA is that it extends the SATA bus

at full speed, which tops out at a theoretical 6 Gbps, whereas the fastest USB

connection (USB 3.0, also called SuperSpeed USB) maxes out at 5 Gbps

SCSI

chains use termination to prevent

this problem. Termination simply

means putting something on the

ends of the wire to prevent this

echo.

Protecting Data with RAID

Ask experienced techs “What is the most expensive part of a PC?” and

they’ll all answer in the same way: “It’s the data.” You can replace any single

part of your PC for a few hundred dollars at most, but if you lose critical

data—well, let’s just say I know of two small companies that went out of

business because they lost a hard drive full of data A better solution, though, would save your data if a hard drive died and

enable you to continue working throughout the process. This is possible if

you stop relying on a single hard drive and instead use two or more drives to store your data.

The data on each

drive would always be identical. One drive would be the primary drive

and the other drive, called the mirror drive, would not be used unless the

primary drive failed. This process of reading and writing data at the same

time to two drives is called disk mirroring

If you really want to make data safe, you can use a separate controller

for each drive. With two drives, each on a separate controller, the system

will continue to operate even if the primary drive’s controller stops working.

This super-drive mirroring technique is called disk duplexing (see Figure

11.35). Disk duplexing is also much faster than disk mirroring because

one controller does not write each piece of data twice

You can use multiple drives

to increase your hard drive access speed. Disk striping (without parity)

means spreading the data among multiple (at least two) drives. Disk striping

by itself provides no redundancy. If you save a small Microsoft Word

file, for example, the file is split into multiple pieces; half of the pieces go on

one drive and half on the other (see Figure 11.36).

The one and only advantage of disk striping is speed—it is a fast way

to read and write to hard drives. But if either drive fails, all data is lost.::::::::::::::But if either drive fails, all data is lost.

You should not do disk striping—unless you’re willing to increase the risk

of losing data to increase the speed at which your hard drives save and

restore data.

Disk striping with parity, in contrast, protects data by adding extra information,

called parity data, that can be used to rebuild data if one of the drives

fails. Disk striping with parity requires at least three drives, but it is common

to use more than three. Disk striping with parity combines the best of

disk mirroring and plain disk striping. It protects data and is quite fast. The

majority of network servers use a type of disk striping with parity.

RAID

redundant array of independent (or inexpensive) disks (RAID).

They outlined seven levels of RAID, numbered 0 through 6::::::::::::::::::;

■RAID 0—Disk Striping Disk striping requires at least two drives.

It does not provide redundancy to data. If any one drive fails, all

data is lost.

■ RAID 1—Disk Mirroring/Duplexing RAID 1 arrays require

at least two hard drives, although they also work with any even

number of drives. RAID 1 is the ultimate in safety, but you lose

storage space because the data is duplicated; you need two 100-GB

drives to store 100 GB of data.

■ RAID 2—Disk Striping with Multiple Parity Drives RAID 2 was

a weird RAID idea that never saw practical use. Ignore it.

■ RAID 3 and 4—Disk Striping with Dedicated Parity RAID

3 and 4 combined dedicated data drives with dedicated parity

drives. The differences between the two are trivial. Unlike RAID 2,

these versions did see some use in the real world but were quickly

replaced by RAID 5.

■ RAID 5—Disk Striping with Distributed Parity Instead of

dedicated data and parity drives, RAID 5 distributes data and

parity information evenly across all drives. This is the fastest way to

provide data redundancy. RAID 5 is by far the most common RAID

implementation and requires at least three drives. RAID 5 arrays

effectively use one drive’s worth of space for parity. If, for example,

you have three 200-GB drives, your total storage capacity is 400 GB.

If you have four 200-GB drives, your total capacity is 600 GB.

■ RAID 6—Disk Striping with Extra Parity If you lose a hard drive

in a RAID 5 array, your data is at great risk until you replace the bad

hard drive and rebuild the array. RAID 6 is RAID 5 with extra parity

information. RAID 6 needs at least five drives, but in exchange you

can lose up to two drives at the same time. RAID 6 is gaining in

popularity for those willing to use larger arrays.

Hybrid Hard Drives

Windows Vista and Windows 7 support hybrid hard drives (HHDs), drives

that combine flash memory and spinning platters to provide fast and reliable

storage, and offer ReadyBoost for faster caching and booting.