Chapter Two Input and Storage Devices Part II: Storage Devices

Chapter Two

Input and Storage DevicesPart 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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• 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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• 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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• 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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• 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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• CDs can store between 650 and 900 MB of data

• CDs can hold 74 to 99 minutes of audio

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• CD speeds depend on their RPMs (revolutions per minute)– 1x speed = 1.23 Mbps– 56x speed = 68.8 Mbps

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• 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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• 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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Flash RAM Storage

• Stores data in static (non-volatile) RAM– USB flash drives– Flash memory cards and readers– Solid-state hard drive– Mobile media devices (iPods, etc.)

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Documents

Chapter Two Input and Storage Devices Part II: Storage Devices