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Guide to Operating Systems,

4thed.

Chapter 7: Using and ConfiguringStorage Devices


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Guide to Operating Systems, 4th ed. 2

Objectives

2

Explain common disk storage technologies

Back up data using operating system tools

Explain network storage technologies

Discuss removable disk storage

Describe tape drive technologies

Explain storage management tools in different

operating systems


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Disk Storage Options

Today, most computers come with one or moreDVD/CD-ROM drives and a fixed hard drive

Removable hard drives and flash drives can be

connected through USB ports and othercommunication channels

Disk refers to a hard drive and disc refers to anoptical medium, such as a CD or DVD


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Disk Storage Options



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Hard Drive Interfaces

In some older PCs, a popular hard drive interface

was the Integrated Drive Electronics (IDE) interface

Enhanced IDE (EIDE)supports higher transfer

speeds, connects up to four devices, and is foundin older PCs American National Standards Institute (ANSI)refers to the

IDE standard as the Advanced Technology Attachment (ATA)

The newer high-speed serial version of the ATAinterface is called Serial ATA (SATA)

External SATA (eSATA)interface that enables

connectivity for an external SATA drive


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Through eSATA you can connect external SATA

drives by plugging into a port or slot interface Interface options include PCMCIA and Express Card

Light Peakan emerging technology that isprojected to be a contender for the USB peripheral

device market (uses an optical connection)

Small Computer System Interface (SCSI)

relatively fast interface that can support up to 8 or16 devices Disks and other SCSI devices are connected together in a

daisy chain fashion


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SCSI (continued)

Each end of the SCSI cable must be electrically terminated to

prevent echoes and ghost signals on the cable

A terminator is an electronic resistor that absorbs the signal

Can be built into a device, such as a disk drive

Advances in SCSI have resulted in several enhancements:

Ultra SCSI, Ultra wide SCSI, Ultra2 SCSI, Ultra2 wide SCSI,

Ultra3 SCSI (Ultra 160), Ultra320 SCSI, and Ultra640 SCSI

Ultra640 transfers at a rate of 640 MBps, has a 16-bit bus, handles

16 devices and used for servers and network storage

Serial Attached SCSI (SAS)new technology that supports up

to 16,256 devices, has initial speeds in the 3-6 Gbps range,

and is compatible with the SATA interface


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SCSI Configuration


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Globally Unique Identifier (GUID) Partition Table

or GPTa new way to partition disks Allows OSs to handle extremely large disks

Windows System Information utility is a way to viewthe hard drive configuration on your computer

Hard disk failures do happen so backing up your

computer is an essential practice

Most OSs today offer Backup utilities that makebacking up data easier Examples of those utilities are listed in the table on the next

slide


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Backup utilities


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Basic and Dynamic DisksWindows OS has the ability

to distinguish between these two disk types

Basica physical hard drive that contains primary and

extended partitions, or logical drives that are known as volumes

Dynamicvolumes that can span multiple disks

Fault tolerance is supportedinvolves implementing software or

hardware to protect against hardware failures, power interruptions,

and lost data

Supported by all editions of Windows Server 2003/R2 and

Windows Server 2008/R2 Supported by some later versions of Windows desktop versions

Basic disks can be converted to dynamic disks by using the Disk

Management tool in Windows


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Solid State Drives (SSD)a storage technology

that uses semiconductors for storage Similar technology is used in flash drives but SSDs are larger

than flash drives and hold more data

Advantages of SSD over traditional hard drives: No moving parts

No sensitive magnetic disks

Faster access to data

More reliable because there are no fragile drive platters

Lower power requirements because there is no motor

Disadvantage: More expensive than traditional hard disk storage


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RAID ArraysRedundant array of inexpensive (or

independent) disks

RAID arrays serve four purposes:

Increased reliability Increased storage capacity

Increased speed

Fault tolerance

Various RAID designs, typically designated asLevel 0Level 5

RAID can be costly and is primarily used on

servers


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RAID is implemented as a combination of hardware

and software Hardwarehard disks connected to a controller (or more than

one)

Softwareprovides an interface to the OS to provide access tospecial RAID features offered

Modern RAID systems offer configuration at the

hardware level (does not need OS to configure

RAID) RAID is covered in more detail in Chapter 11



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CD, DVD, and Blu-Ray

Compact Disc (CD) Technologya polycarbonate

plastic disc that has a reflective optical surface that

can be read by a laser

CD-ROMcompact disc read-only memory uses atechnology in which information is pressed onto the

disc one time (read or played many times)

CD-Rcompact disc recordableinformation can

be burned onto the disc by a laser one time Commonly called burning a disc

CD-RWcompact disc rewriteableyou can write

to the disc many times


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CDs store data in a big spiral instead of tracks and

sectors like hard disks

When a disc is read:

Laser light is emitted by the CD-ROM drive head and reflectedoff the disc surface onto an optical pickup

Surface is covered with indentations or pits, depending on the

size of the pits, ones or zeros are returned

The surface of the CD reflects light during a data read

operation CDs are very sensitive to scratches and other kinds

of damages that can hinder optical readout


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Data on the CD can employ any or all of the

following error recovery methods: Paritysimple error detection method that typically counts the

number of nonzero bits in a string of data, then sets a parity bit

to reflect whether the bits total to an even or odd number

Error correction code (ECC)can replace errors by adding

duplicate data or parity data so missing data can be recovered

Error concealmentuses surrounding data to help calculate

approximate data to fill in for the missing data

Cyclic redundancy check code (CRCC)uses an algebraic

polynomial and error key to detect and overcome errors

Reed-Solomon R-S codesuses a complex polynomial

technique for addressing data errors


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A standard CD holds 737 MB of user data, but

counting space for error detection the true storage

capacity is about 847 MB

CDs are rated in terms of recording minutes as wellas megabytes of data because they are used for

music or audio as well as for data

Rotational speeds of CD-ROM drives range from

the normal speed of 200-500 revolutions perminute to as high as 72 times that speed (72X)


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Digital video disc (DVD)works a lot like a CD but

storage capacity and data transfer rate of a DVD

are much higher than for a CD

DVDs can store information on two sides with up to

two layers per side Unlike CDs, DVDs have a second layer that is read by using

light that hits the disk at a different angle

A single-layer single-sided DVD holds 4.7 GB of

data A double-layer single-sided DVD holds 8.54 GB and a double-

layer double-sided DVD holds up to 17.08 GB of data



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Recordable and Rewritable DVDs Digital video disc-recordable (DVD-R)

Digital video disc+recordable (DVD+R)


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DVD drives and media


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DVD/CD-ROM Drives

Usually connected to a computer using a hard disk

interface

Most PCs use the SATA, EIDE, or SCSI interface

Require different drivers than hard disk drives

Most PCs have drivers built into the BIOS system and

boot system

This enables computers to boot an OS from a CD or DVD

Most PCs can boot an OS directly from a CD or DVD forinitial installation



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Blu-Ray Drives Blu-ray discs are different from DVD/CD-ROM because the

data is recorded on top of the polycarbonate layer

Enables the information on the disc to be read more accurately

without the problem of disc tilt

Data transfer speed can reach 36 MBps (compared to about 10

MBps for DVDs)

Current storage capacity of a disc is a maximum of 50 GB

Connected to computers using a SATA interface

To play a Blu-ray video on a computer, you must have a video

display compatible with High-bandwidth Definition Content

Protection (HDCP)


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Network Storage and Cloud Storage

Organizations today are dealing with massive

amounts of data Backups, disaster recovery, and availability of data are reasons

why storage area networks and cloud storage are growing in

popularity

Storage Area Networks (SAN)a grouping of

storage devices that form a small private network Data transfer between servers and storage systems takes

place on Fibre Channel Typical speed for most Fibre Channels is 8 Gbps (16 and 40

Gbps under development)


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InfiniBanddesigned for ultrafast connectivity in

data centers, such as linking servers for clustering

to act as one powerful server

Emerged as an alternative to Fibre Channel Network attached storage (NAS)a way to directly

attach storage to a local area network (LAN) Works with multiple OSs

Allows most clients to access the storage on the network usingTCP/IP (standard network communications protocol)

Different than a SANservers communicate with the storage

over the main network rather than by a separate Fibre Channel


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NAS can use Internet Small Computer System

Interface (iSCSI) for communications Offers TCP/IP-based communication that enables connectivity

with SCSI-based storage arrays

Faster data access than Fibre Channel because data

transmission speeds are linked to the actual speed of the

network

Because it uses TCP/IP, can be used on LANs, WANs, or over

the Internet

Disadvantage: creates extra network traffic which can lead to

network congestion


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Network attached storage (NAS)


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Cloud Storageavailable through the Internet orthrough Web-based applications Data may be transferred over the Internet or network to the

users computer or user can manipulate data on a remote

computer via the Internet Users data is available from any location where Internet is

available

Provides fault tolerance

Examples: YouTube hosts millions of video files, Google Docs

stores document files and spreadsheets Files can be made public or kept private



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Removable Disks

Early examples were floppy disks and Zip disks Storage capacities from 1.44 MB750 MB

Today, users expect removable storage capacities

to match hard disk capacities Some removable hard disks that connect to USB ports can hold

over 1 TB of data

Another removable disk option: SSD Connects to the computer through a USB port

Other options: eSATA and Light Peak (mentioned earlier in this chapter)


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USB Flash Drives

Flash drives or thumb drivesplug into a USB port

and have no internal moving parts Dont require additional drivers and are quickly recognized by

PnP

Easy to use and fit in your pocket

Typical sizes (at this writing) include 4, 8, 16, 32, and 64 GB

Work with Windows, UNIX/Linux, and Mac OS X


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USB Flash Drives

Storage media capacities and life spans



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Tapes and Tape Drives

Tape backup systems are a traditional choice forbacking up large amounts of data

Use magnetic storage and record data in

sequential order Disadvantageto find a file near the end of the tape, drive

must first go through all of the data recorded prior to that file

Access to data is typically slower than a removable hard drive

Most popular for long-term storage

With disk drives growing into terabytes, tape drive technology iscontinuing to evolve in order to keep up



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Tape media capacities



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DAT Drives - Digital audio tape Use a 4-mm tape and the digital data storage (DDS) format

DDS-1 has a capacity of 2 GB (4 GB compressed)

Current standard is DDS-5storage capacity of 36 GB (72 GB

compressed) Backward compatiblecan upgrade to a DDS-5 drive and still

read DDS-4 tapes

Rated at an archival life of 10 years

Still used for audio recordings, but use for data storage is

mostly replaced by other tape technologies



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DLT DrivesDigital linear tape Use half-inch wide magnetic tapes

Record data in tracks

Offers a high-speed search capabilitya file can be found in a

few seconds to a little over a minute Used in many automated tape backup systems

SDLT DrivesSuper digital linear tape Use both magnetic and optical recording methods

Laser technology can more accurately write data to the tapeand allows for greater density of information

Up to 2.4 TB compressed

Both DLT and SDLT have an archival life of up to

30 yearsGuide to Operating Systems, 4th ed. 36


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AIT DrivesAdvanced intelligent tape (AIT) First introduced in 1996 and used mainly in midrange servers

Tapes have an erasable memory chip inside the cartridge that

stores information normally written at the beginning of the tape

Can fast forward and pinpoint information faster Started out with a capacity of 35/90 GB

S-AIT DrivesSuper advanced intelligent tape Has a capacity of 500 GB/1.3 TB (native/compressed)

Both of these drives can sustain up to 30,000 tapepasses and have an archival life of 30 years



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Storage Management Tools

Windows Disk Management tool in Windows 7



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Disk Management Tools in UNIX/Linux Common command-line utilitities: fdisk, format, sfdisk, and

cfdisk

sfdisk and cfdiskenable you to verify partitions, list information

about partitions, and repartition a disk Command-line utility mountmounts a file system so that you

can use a disk partition

Many need to manually mount file systems for DVD/CD-ROM or

flash drives

In Linux with the GNOME desktop, there are GUI tools tomanage disk storage



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GNOME Disk Utility


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Summary of UNIX/Linux disk management

commands



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Mac OS X Disk Utilityavailable to partition,format, and manage hard drives, DVD/CD-ROM

drives, removable hard drives, flash drives, and

other storage

Options available depend on the type of storage mediumselected

When you select a storage medium in the left pane, the utility

displays appropriate tabs for the actions you can perform on that

storage medium

Because Mac OS X is UNIX-based, you can alsoopen a terminal window and use the mount

command to manage storage media



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Mac OS X Snow Leopard Disk Utility



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Chapter Summary

This chapter provides an introduction to how OSs interface withstorage devices and gives an overview of storage device

technologies

Popular computer storage technologies include hard disk drives,

solid state drives, RAID arrays, CD, DVD, and Blue-Ray

technologies that interface to the computer through the OS anddevice drivers

An important part of learning to manage hard disk storage is

performing backups

Network storage devices include storage area networks (SANs)

and network attached storage (NAS)

Cloud storage enables users to access storage through the

Internet or a network using Web-based interfaces



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Chapter Summary

SANs can use Fibre Channel or InfinitBand technology andNAS can use iSCSI storage technology

Modern medium- to large-capacity removable storage

includes USB attached removable hard drives, USB solid

state drives, eSATA drives, Light Peak drives, and USB flashdrives

Common tape storage options include DAT, DLT, SDLT,

AIT, S-AIT, and LTO tapes and drives

Operating systems come with storage management tools,

such as the Windows Disk Management tool, the Disk Utilityin GNOME for Linux, and the Mac OS X Disk Utility

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