Input Devices Output Devices Storage Devices Communication Devices Processing Unit.
Chapter Two Input and Storage Devices Part II: Storage Devices.
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Transcript of Chapter Two Input and Storage Devices Part II: Storage Devices.
© 2006-2011 Wiley, Inc. All Rights Reserved.
Strata Objectives Covered
1.1 Identify basic IT vocabulary– USB, PS/2
1.3 Explain the characteristics and functions of internal and external storage devices
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Measurements of Storage Capacity
Size Equals Example
Byte 8 bits One character of text
Kilobyte (KB) 1,024 bytes A 1,000-character plain text file or a tiny graphic
Megabyte (MB) 1,024 KB 600 x 600 photo or one minute of a music clip
Gigabyte (GB) 1,024 MB Full length audio CD is 800 GB, a two-hour DVD movie is 4GB
Terabyte (TB) 1,024 GB Large business database
Petabyte (PB) 1,024 TB All the data for an entire government
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Maximum Storage Capacities
Media Format Largest as of 2011
Standard mechanical hard disk 3 TB
Solid state drive 2 TB
USB flash drive 256 GB
Compact flash card 128 GB
CD 900 MB
Blu-Ray 50 GB
Double-sided, double-density DVD
17 GB
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Hard Disk Drive
• Sealed stack of metal platters• Read-write heads on a retractable
arm• Magnetizes bits of iron oxide
particles on the platters in patterns of positive and negative polarity
• Platters rotate at a high speed
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Hard Disk Drive
• Can be internal or external• Most computers have at least one
internal hard disk drive• External ones use USB or FireWire
(IEEE 1394) connector• Capacities ranging from a few
hundred gigabytes (GB) to 3 terabytes (TB)
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Types of Hard Drive Connectors
• Parallel ATA (PATA)– Traditional interface– 40-pin ribbon cable– Drives use a traditional Molex power
connector
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Types of Hard Drive Connectors
• Serial ATA (SATA)– Newer interface, faster– SATA cable is thinner and less bulky– Seven-wire plug– Drives use a special power connector
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Types of Hard Drive Connectors
• Small Computer System Interface (SCSI)– Uses wider ribbon cable than PATA– Controller on board, not on drive– Less common in desktops– More common in servers and RAIDs– Drives use a traditional Molex power
connector
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Factors that Govern Hard Disk Speed
• Rotational Speed– Measured in Revolutions Per Minute
(RPM)
• Cache Size• Interface Type
– Serial ATA– Parallel ATA– SCSI– USB– FireWire
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RAID
• Redundant Array of Independent Disks– RAID 0 combines multiple devices to
make one large drive, increasing performance
– RAID 1 mirrors the content of one drive on another, increasing reliability
– RAIDs 2 through 6 (5 is most common) increase both performance and reliability by striping data across three or more disks
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Low-Level Formatting
• Done at the factory when the disk is manufactured
• Defines the number of cylinders, heads, and sectors on the drive, which collectively determine its capacity
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Low-Level Formatting
• Because of addressing translation schemes, the physical number of heads, cylinders, and sectors may be different than what’s reported on the drive’s label
• When configuring a drive, use the values on its label
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Low-Level Formatting
• Cylinders: Number of unique positions of the read/write heads Same as number of tracks– A track is a concentric ring on an
individual side of a platter– A cylinder is the collection of tracks at a
certain read/write head position
• Heads: Number of platter sides• Sectors: Number of segments that
each track is divided into
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Partitioning a Disk
• Primary partition– All disks have one– Only the primary partition is directly
bootable– A primary partition can have only one
logical drive
• Extended partition– Optional, not all disks have one – Each extended partition can have one or
multiple logical drives
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Partitioning a Disk
Partitioning a disk creates a master boot record (MBR)
– Contains information about each partition and logical drive
– The OS looks to the MBR to determine what drive letters you have
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Partitioning a Disk
Partitioning requires a disk management utility
– Windows Setup– Disk Management (in Windows)– FDISK (in DOS and earlier Windows
versions)– DISKPART (in Windows Recovery
Console)
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High-Level Formatting
• Creates a filing system compatible with the OS
• NTFS is used for Windows-based systems
• Creates a Master File Table (MFT), a TOC for the logical drive
• Creates a volume boot record, storing info needed to boot from that drive
• Creates a root directory
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High-Level Formatting
• Sectors are grouped into clusters• Also called allocation units• Clusters are the smallest
addressable unit in the file system• Depending on the disk size and file
system, a cluster can be from 1 to 128 sectors
• Each sector holds 512 bytes
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Creating Network Shares
• A network share is a shared network location, such as a drive or folder
• You can share a location on:– A file server– A user PC– Network attached storage (NAS)
• There are security and privacy risks whenever you share data
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Compact Discs and Drives
• Widely used for music and software distribution
• Optical media• Store data in patterns of more and
less reflective areas (lands and pits)
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Compact Discs and Drives
• CDs can store between 650 and 900 MB of data
• CDs can hold 74 to 99 minutes of audio
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Compact Discs and Drives
• CD speeds depend on their RPMs (revolutions per minute)– 1x speed = 1.23 Mbps– 56x speed = 68.8 Mbps
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Compact Discs and Drives
• Constant linear velocity– Data is read at a consistent rate– Disc spins at different speeds
depending on where on the disc the data is located
• Constant angular velocity– Disc spins at a consistent speed– Data read rate depends on where on the
disc the data is located
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Compact Discs and Drives
• CD and DVD interfaces– PATA– SATA– SCSI– USB (external)
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CD Writing Technologies
• Compact Disc Recordable– Can be written to once– Laser etches the die on the surface of
the disc, making some areas less reflective to simulate pits
• Compact Disc Rewriteable– Can be written to, erased, and reused– Uses different laser write settings:
• High: Makes an area less reflective• Low: Causes an area to go back to its
original reflectivity
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DVD Disc and Drives
• Digital versatile disc, or digital video disc
• Single-sided, single-layer holds 4.7 GB of data
• Each disc can have up to two sides and up to two layers
• Two competing write technologies– DVD+R, DVD+RW– DVD-R, DVD-RW
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Blu-Ray Discs and Drives
• Similar to DVDs but can hold more data
• Use a blue laser rather than a standard red one
• Can hold 25GB per layer
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