Transcript Using and Configuring Storage Devices

Guide to Operating Systems,
4th ed.
Chapter 7: Using and Configuring
Storage Devices
Objectives
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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 more
DVD/CD-ROM drives and a fixed hard drive.
• These storage devices are mounted in the
computer case and connect to the computer
hardware through the internal cable system.
• 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
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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.
– IDE supports connecting two devices into the IDE interface.
• Enhanced IDE (EIDE) – supports higher transfer
speeds, connects up to four devices, and is also
found in older PCs.
– The IDE interface was formalized in 1990 as an American
National Standards Institute (ANSI) standard.
– ANSI refers to the IDE standard as the Advanced Technology
Attachment (ATA) interface standard.
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Hard Drive Interfaces
• An ATA interface (IDE standard) uses a parallel
connection.
– A connection that sends data and control information over wires
connected in parallel so that multiple data bits are sent at one
time.
• Parallel ATA (PATA)
• In a PATA interface, the cable has 40 active conductors (wires),
although some ATA cables actually have up to 80 wires, even
though only 40 are used.
• The newer high-speed serial version of the ATA
interface is called the Serial ATA (SATA).
– Uses a high-speed serial cable to achieve transfer speeds
currently up to 6 Gbps.
– A SATA cable interface has seven conductors.
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Hard Drive Interfaces
• Besides speed, another advantage of using SATA
hard drives is that the cabling takes up less space
inside the computer, allowing more room for
computer cards and enabling better air flow for
cooling the computer through internal fans.
• The SATA technology led to External SATA
(eSATA)
– An interface that enables connectivity for an external SATA
drive.
– Through eSATA you can connect external SATA drives by
plugging into an appropriate port or slot interface.
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Hard Drive Interfaces
• Current interface options include:
– PCMCIA and ExpressCard ports
– A regular Peripheral Component Internet (PCI) card slot for an
eSATA drive
• eSATA competes with other external storage
connection technologies such as USB, FireWire,
and Light Peak.
• Light Peak – an emerging technology that is
projected to be a contender for the USB peripheral
device market.
– USB-connected hard drives use a copper wire connection.
– Light Peak uses an optical cable.
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Hard Drive Interfaces
• Light Peak (contid).
– USB 3.0 currently carries data at q top speed of 4.8 Gbps.
– Initial Light Peak data transfer rates can presently reach about
10 Gbps and are eventually expected to go up to 100 Gbps.
– Another advantage of Light Peak is that signal loss and
interference on an optical cable are very small compared to
copper USB cable.
• Small Computer System Interface (SCSI) – A
relatively fast interface, that tends to be more
expensive than PATA or SATA drives.
• Each SCSI interface can support up to 8 or 16
devices (including the controller), depending on the
type of SCSI.
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Hard Drive Interfaces
• SCSI (continued)
– The disks or other SCSI devices are connected together in a daisy
chain fashion.
– Each end of the SCSI cable must be electrically terminated to
prevent echoes and ghost signals on the cable.
• Either a disk drive or an external terminator typically terminates
the other end of the chain.
• A terminator is an electronic resistor that absorbs the electronic
signal so that the signal is not reflected back onto the cable.
– Can be built into a device, such as a disk drive or a small apparatus
that is plugged into the cable externally.
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Hard Drive Interfaces
SCSI Configuration
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Hard Drive Interfaces
• SCSI (continued)
– 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 the potential of up to 12 Gbps.
• SAS is compatible with the SATA interface which is useful for
server and storage flexibility.
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Hard Drive Interfaces
• The number of platters, heads, tracks, and sectors
per track varies widely from hard disk to hard disk.
• Many OSs keep a table somewhere on the disk
that describes the disk in great detail.
– This includes the Master Boot Record (MBR) and partition table
which are at the beginning track and sectors of a disk.
• The MBR has information about partitions and how to locate them.
• The partition table has information about each partition on a disk:
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–
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Partition type
Size
Location
Which partition to access first to start the OS.
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Hard Drive Interfaces
• Globally Unique Identifier (GUID) Partition Table
or GPT
– A newer way to partition disks
– Does not have the same limits on the number of partitions as
MBR
– Each partition has a unique GUID in a structure that helps
ensure partition identification is not subject to errors
– Allows OSs to handle extremely large disks.
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Hard Drive Interfaces
• 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.
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Hard Drive Interfaces
Backup utilities
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Hard Drive Interfaces
• 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.
• Dynamic disks make it possible to set up up to 2000 dynamic
volumes on one disk (Microsoft recommend 32 or fewer volumes
per disk.
• Dynamic disks also have the ability to extend volumes onto
additional physical disks.
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Hard Drive Interfaces
– Dynamic (contid.)
• 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
• SSD drives of over 250 GB are available, but because of expense,
it is more common to see drives in configurations of 60 – 120 GB.
• Advantages of SSD over traditional hard drives:
– No moving parts
– No sensitive magnetic disks
– Faster access to data (over 50%), because there is no need to
spin a drive.
– More reliable because there are no fragile drive platters
– Lower power requirements because there is no motor
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Hard Drive Interfaces
• Solid State Drives (SSD) (contid.)
– Disadvantage:
• More expensive than traditional hard disk storage
• SSD drives are particularly attractive for use in
laptop computers because of the reduced power
consumption.
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Hard Drive Interfaces
• Researchers at the University of California
(Berkeley) introduced the concept of a redundant
array of inexpensive (or independent) disks
(RAID) to use multiple disks in a storage array.
• RAID arrays serve four purposes:
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Increased reliability
Increased storage capacity
Increased speed
Fault tolerance
• RAID uses various designs, typically designated as
Level 0 – Level 5 and multiple disks to reduce the
chance of information being lost in the event of a
hardware failure.
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Hard Drive Interfaces
• Because RAID array implementation tends to be
costly, RAID storage is used primarily on servers,
with the exception of some desktop systems that
are critical to a business or research function.
• RAID is implemented as a combination of hardware
and software.
– Hardware – hard disks connected to a controller (or more than
one)
– Software – can be a low-level device driver that works with any
RAID hardware and provides an interface to the OS to provide
access to the special RAID features offered.
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Hard Drive Interfaces
• Modern RAID systems multiple disks, offer RAID
configuration capabilities at the hardware level,
which to the user means that different RAID
approaches can be configured at the hardware
level regardless of whether the OS has features to
configure RAID.
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CD, DVD, and Blu-Ray
• Compact Disc (CD) Technology
– A compact disc (CD) is a polycarbonate plastic disc that has a
reflective optical surface that can be read by a laser.
– The compact disc read-only memory (CD-ROM) uses a
technology in which information is pressed onto the disc one
time so that it can be read or played many times.
• Generally used for mass distribution of software or music.
• Can be written to one time.
• Compact Disc Recordable (CD-R)
– A compact disc recordable create by burning the information
by a laser (“burning a disc”)
• Similar to a CD, the data is written one time and read time after
time.
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CD, DVD, and Blu-Ray
• Compact Disc Rewriteable (CD-RW)
– Enables you to record information from your computer.
– You can write to a CD-RW many times.
• Each time you rewrite to a CD-RW, the information on the disc has
to be “blanked” (erased) prior to writing on the CD again.
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CD, DVD, and Blu-Ray
• CDs store data in a big “spiral” instead of tracks and
sectors like hard disks.
– The spiral starts at the inside of the disc and winds itself slowly
towards the outside of the disc.
• 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.
– The surface of the disc is covered with indentations (pits) that
shift the position of the reflected laser light as it is returned to
the pickup.
– 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:
– Parity – A simple error detection method that typically counts
the number of nonzero bits in a string of data and then sets a
parity bit to reflect whether the number of nonzero bits total to
an even or an odd number.
• If the total is an even number, it sets the parity bit (equal to 1).
• If the total is odd, it does not set the parity bit (equals 0).
– Error correction code (ECC) – Can replace errors by adding
duplicate data or parity data so that missing data can be
recovered.
– Error concealment – Uses surrounding data to help calculate
approximate data to fill in for the missing data.
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CD, DVD, and Blu-Ray
• Data on the CD can employ any or all of the
following error recovery methods (contid.):
– Cyclic redundancy check code (CRCC) – Uses an algebraic
polynomial and error key to detect and overcome errors.
– Reed-Solomon R-S codes – An error detection and correction
technique developed by Irving Reed and Gustave Solomon that
uses a complex polynomial technique for addressing data
errors.
• All five of these error recovery methods are also
used on DVDs.
• Although the CD is a relatively delicate medium, its
built-in error detection and correction make it one
of the most reliable.
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CD, DVD, and Blu-Ray
• A standard CD (CD-ROM, CD-R, CD-RW) holds
737 MB of user data, but counting space for error
detection information the true storage capacity is
about 847 MB.
– The actual storage capacity on a CD depends on the recording
minutes for that CD, which can be from 21 minutes (184.6 MB)
to 99 minutes (870.1 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.
• CDs are single-sided discs.
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CD, DVD, and Blu-Ray
• The rotational speeds of CD-ROM drives range
from the normal speed of an audio CD (200-500
revolutions per minute) to as high as 72 times that
speed (72X).
• High-speed CD-ROM drives can attain data
transfer rates of 88.5 Mbps.
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CD, DVD, and Blu-Ray
• Digital video disc (DVD) – works a lot like a CD.
– It is also optical medium, and it has the data written in the form
of a spiral of blocks.
– All data is read from the disc with the use of a laser and an
optical pickup.
• The 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.
– On a CD, when laser light hits the layer, it is reflected.
– On a DVD, the same thing happens, but, in addition to the first
layer, which is a spiral that moves from the middle of the disc to
the outside, the DVD has a second layer.
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CD, DVD, and Blu-Ray
• DVDs can store information on two sides with up to
two layers per side.
– The second layer is read by using light that hits the disk at a
different angle.
– The second layer is also a spiral that is written from the outside
of the disc to the inside.
• DVDs come in two diameters:
– 8 cm (mini DVD)
– 12 cm (standard size DVD)
– Each side of a 12 cm DVD can contain up to two layers and
each layer can hold 4.7 GB of data.
• A single-layer single-sided DVD holds 4.7 GB of data
• A double-layer single-sided DVD holds 8.54 GB and a doublelayer 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
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 for
initial 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 but just
under the hard coating that protects the disc from damage.
• Enables the information on the disc to be read more accurately
without the problem of “disc tilt”.
– Errors resulting from a disc not being perfectly flat.
– Data transfer speed can reach 36 MBps (compared to about 10
MBps for DVDs).
– Current storage capacity of a Blu-Ray disc is a maximum of 50
GB.
– This technology has the potential to reach 500 GB with the use
of ultraviolet layers.
– Connected to computers using a SATA interface
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CD, DVD, and Blu-Ray
• Blu-Ray Drives
– To play a Blu-ray video on a computer, you must have a video
display system (graphics card and monitor) compatible with
High-bandwidth Definition (Digital) Content Protection
(HDCP).
• A digital copy protection method that helps ensure digital content
cannot be pirated.
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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.
– Directly connects servers and storage systems without sending
data over the larger or corporate network.
– Accomplished by tying the servers and storage systems
together via a switched , full-duplex (data goes in both
directions at the same time) Fibre Channel connection.
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Network Storage and Cloud Storage
• Storage Area Networks (SAN)
– Typical speed for most Fibre Channel’s is 8 Gbps (16 and 40
Gbps under development).
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Network Storage and Cloud Storage
Storage area network (SAN)
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Network Storage and Cloud Storage
• InfiniBand – Challenging the Fibre Channel
architecture.
– 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 for connecting
external disk arrays of storage in SANs.
– Uses high speed (fabric switching) for fast data transmission of
up to 300 Gbps.
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Network Storage and Cloud Storage
• 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
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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
• Transmission Control Protocol/Internet Protocol
– The basic communication (protocol) language of the Internet
– 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 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 the user can access and manipulate data on
a remote computer accessed via the Internet or a web-based
application.
– User’s data is available from any location where the Internet or
private network is available.
– Provides fault tolerance.
• If a hard drive fails, the data is still available from another hard
drive or RAID array.
– 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 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
• A removable hard disk is a traditional hard disk with
platters, heads, and a motor, and the data is
magnetically recorded on platters.
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Removable Disks
• Another removable disk option: SSD (Solid State)
– Connects to the computer through a USB port
• When a USB 3.0 port is available (10 times the speed of USB 2.0)
this removable disk technology offers the fastest data transport.
– This solution can be advantageous in situations where time is
critical or in which the removable drive is subject to harsh
conditions.
• Other options:
– eSATA and Light Peak (mentioned earlier in this chapter)
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USB Flash Drives
• Flash drives or thumb drives – plug into a USB
port and have no internal moving parts.
– Data can be written, deleted, and modified.
– 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
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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 for
backing up large amounts of data.
• Tapes use magnetic storage and record data in
sequential order.
– Disadvantage – to find a file near the end of the tape, the 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
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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-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
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Tapes and Tape Drives
• DLT Drives – Digital linear tape
– Use half-inch wide magnetic tapes
– Record data in tracks that run the whole length of the tape.
• Each tape contains 128, 168, 208, 240, 352, or 488 tracks and the
data is recorded on the first track from the beginning to the end of
the tape.
• Then the tape is reversed and the data is written from the end to
the beginning.
– 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
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Tapes and Tape Drives
• 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 years
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Tapes and Tape Drives
• 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
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Tapes and Tape Drives
• LTO Drives – Linear tape open
– Most widely accepted in high-end servers because of highspeed 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
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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
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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 utilities for managing, formatting, and
partitioning disks on UNIX/Linux systems are:
• fdisk / format – Format Disk
• sfdisk / cfdisk – Utilities that enable you to verify partitions, list
information about partitions, and to repartition a disk.
– Command-line utility mount – mounts a file system so that you
can use a disk partition
• Ma
• 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
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Storage Management Tools
Summary of UNIX/Linux disk management
commands
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Storage Management Tools
GNOME Disk Utility
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Storage Management Tools
• 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.
– To open the Disk Utility:
•
•
•
•
Ensure Finder is open;
Click the Go menu;
Click Utilities;
Double-click Disk Utility.
– When you select a storage medium in the left pane, the Disk
Utility displays the appropriate tabs for the actions you can
perform on that storage medium.
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Storage Management Tools
• Mac OS X Disk Utility
– When you select a storage medium in the left pane, the Disk
Utility displays the appropriate tabs for the actions you can
perform on that storage medium.
– For a hard disk you can:
•
•
•
•
•
Repair the disk using the First Aid option;
Erase the contents;
Partition and format the disk;
Set up RAID on the disk;
Restore a disk image or volume.
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Storage Management Tools
Mac OS X Snow Leopard Disk Utility
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Storage Management Tools
• Mac OS X Disk Utility
– For removable media you can use the Disk Utility to mount
media, eject media, burn a CD/DVD, and perform other actions.
– Because Mac OS X is UNIX-based, you can also open a
terminal window and use the mount command to manage
storage media.
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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
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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
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