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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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Guide to Operating Systems, 4th ed. 3
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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Hard Drive Interfaces
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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Hard Drive Interfaces
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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Hard Drive Interfaces
SCSI Configuration
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Hard Drive Interfaces
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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Hard Drive Interfaces
Backup utilities
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Guide to Operating Systems, 4th ed. 11
Hard Drive Interfaces
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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Hard Drive Interfaces
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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Hard Drive Interfaces
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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Hard Drive Interfaces
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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CD, DVD, and Blu-Ray
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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CD, DVD, and Blu-Ray
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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CD, DVD, and Blu-Ray
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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CD, DVD, and Blu-Ray
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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CD, DVD, and Blu-Ray
Recordable and Rewritable DVDs Digital video disc-recordable (DVD-R)
Digital video disc+recordable (DVD+R)
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CD, DVD, and Blu-Ray
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DVD drives and media
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CD, DVD, and Blu-Ray
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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CD, DVD, and Blu-Ray
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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Network Storage and Cloud Storage
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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Network Storage and Cloud Storage
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 Storage and Cloud Storage
Network attached storage (NAS)
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Network Storage and Cloud Storage
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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Tapes and Tape Drives
Tape media capacities
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Tapes and Tape Drives
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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Tapes and Tape Drives
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
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Tapes and Tape Drives
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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Storage Management Tools
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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Storage Management Tools
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GNOME Disk Utility
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Storage Management Tools
Summary of UNIX/Linux disk management
commands
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Storage Management Tools
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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Storage Management Tools
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