9781111306366 ppt ch7

Guide to Operating Systems,
4th
ed.
Chapter 7: Using and Configuring
Storage Devices

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

Disk Storage Options
• Today, most computers come with one or more
DVD/CD-ROM drives and a fixed hard drive
• Removable hard drives and flash drives can be
connected through USB ports and other
communication channels
• “Disk” refers to a hard drive and “disc” refers to an
optical medium, such as a CD or DVD

Disk Storage Options

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 found
in 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 ATA
interface is called Serial ATA (SATA)
• External SATA (eSATA) – interface that enables
connectivity for an external SATA drive

• Through eSATA you can connect external SATA
drives by plugging into a port or slot interface
– Interface options include PCMCIA and Express Card
• Light Peak – an emerging technology that is
projected 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 or
16 devices
– Disks and other SCSI devices are connected together in a
daisy chain fashion

• 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

SCSI Configuration

• Globally Unique Identifier (GUID) Partition Table
or GPT – a new way to partition disks
– Allows OSs to handle extremely large disks
• Windows System Information utility is a way to view
the 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 make
backing up data easier
– Examples of those utilities are listed in the table on the next
slide

Backup utilities

• Basic and Dynamic Disks – Windows OS has the ability
to distinguish between these two disk types
– Basic – a physical hard drive that contains primary and
extended partitions, or logical drives that are known as
volumes
– Dynamic – volumes that can span multiple disks
• Fault tolerance is supported – involves 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

• 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

• RAID Arrays – Redundant 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 as
Level 0 – Level 5
• RAID can be costly and is primarily used on
servers

• RAID is implemented as a combination of hardware
and software
– Hardware – hard disks connected to a controller (or more than
one)
– Software – provides an interface to the OS to provide access to
special 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

CD, DVD, and Blu-Ray
• Compact Disc (CD) Technology – a polycarbonate
plastic disc that has a reflective optical surface that
can be read by a laser
• CD-ROM – compact disc read-only memory uses a
technology in which information is pressed onto the
disc one time (read or played many times)
• CD-R – compact disc recordable – information can
be burned onto the disc by a laser one time
– Commonly called “burning a disc”
• CD-RW – compact disc rewriteable – you can write
to the disc many times

• 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 reflected
off 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

• Data on the CD can employ any or all of the
following error recovery methods:
– Parity – simple 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 concealment – uses 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 codes – uses a complex polynomial
technique for addressing data errors

• 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 well
as 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 per
minute to as high as 72 times that speed (72X)

• 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

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

DVD drives and media

• 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 for
initial installation

• 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)

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 Channel’s is 8 Gbps (16 and 40
Gbps under development)

Storage area network (SAN)

• InfiniBand – designed 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 using
TCP/IP (standard network communications protocol)
– Different than a SAN – servers communicate with the storage
over the main network rather than by a separate Fibre Channel

• 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

Network attached storage (NAS)

• Cloud Storage – available through the Internet or
through Web-based applications
– Data may be transferred over the Internet or network to the
user’s computer or user can manipulate data on a remote
computer via the Internet
– User’s 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

Removable Disks
• Early examples were floppy disks and Zip disks
– Storage capacities from 1.44 MB – 750 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)

USB Flash Drives
• Flash drives or thumb drives – plug into a USB port
and have no internal moving parts
– Don’t 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

USB Flash Drives
Storage media capacities and life spans

Tapes and Tape Drives
• Tape backup systems are a traditional choice for
backing up large amounts of data
• Use magnetic storage and record data in
sequential order
– Disadvantage – to 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
is continuing to evolve in order to keep up

Tape media capacities

• 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-5 – storage capacity of 36 GB (72 GB
compressed)
– Backward compatible – can 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

• DLT Drives – Digital linear tape
– Use half-inch wide magnetic tapes
– Record data in tracks
– Offers a high-speed search capability – a file can be found in a
few seconds to a little over a minute
– Used in many automated tape backup systems
• SDLT Drives – Super digital linear tape
– Use both magnetic and optical recording methods
– Laser technology can more accurately write data to the tape
and 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

• AIT Drives – Advanced 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 Drives – Super advanced intelligent tape
– Has a capacity of 500 GB/1.3 TB (native/compressed)
• Both of these drives can sustain up to 30,000 tape
passes and have an archival life of 30 years

• LTO Drives – Linear tape open
– Most widely accepted in high-end servers (because of high-
speed performance)
– Standards are open to the public and are nonproprietary
– LTO Ultrium format was developed so that LTO tapes can be
used in existing DLT tape drives
• For faster conversion to LTO Ultrium technology
– Offer fast data transfer speed of up to 240 MBps, for
noncompressed data and 120 MBps for compressed data
– Can sustain up to 260 tape passes and have an archival life of
15-30 years

Storage Management Tools
• Windows Storage Management Tools
– Windows Disk Management tool for hard drive and removable
storage is available in the following versions:
• Windows XP/Vista/7, Server 2003/R2, and Server 2008/R2
– Enables you to:
• Create, format, and delete partitions
• Manage partitions
• Manage removable storage such as hard drives, DVD/CD-ROM
drives, and flash drives
• Convert a basic disk to a dynamic disk
– Can access this tool from Computer Manager
– Other utilities are Disk Defragmenter, chkdsk, and format

Windows Disk Management tool in Windows 7

• Disk Management Tools in UNIX/Linux
– Common command-line utilitities: fdisk, format, sfdisk, and
cfdisk
– sfdisk and cfdisk enable you to verify partitions, list information
about partitions, and repartition a disk
– Command-line utility mount – mounts 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 to
manage disk storage

GNOME Disk Utility

Summary of UNIX/Linux disk management
commands

• Mac OS X Disk Utility – available 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 medium
selected
• 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 also
open a terminal window and use the mount
command to manage storage media

Mac OS X Snow Leopard Disk Utility

Chapter Summary
• This chapter provides an introduction to how OSs interface with
storage 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 and
device 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

Chapter Summary
• SANs can use Fibre Channel or InfinitBand technology and
NAS 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 flash
drives
• 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 Utility
in GNOME for Linux, and the Mac OS X Disk Utility

9781111306366 ppt ch7

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