COM113 Introduction to Computing

Storage

Storage Objectives

Differentiate between storage devicesand storage media

Differentiate between storage devicesand storage media

Describe the characteristics ofmagnetic disks

Describe the characteristics ofmagnetic disks

Describe the characteristics of a hard disk

Describe the characteristics of a hard disk

Discuss various types of miniature, external, and removable hard disksDiscuss various types of miniature, external, and removable hard disks

Describe the characteristics of optical discs

Describe the characteristics of optical discs

Differentiate among CD-ROMs,recordable CDs, rewritable CDs,

DVD-ROMs, BD-ROMs, HD DVD-ROMs, recordable DVDs, and

rewritable DVDs

Differentiate among CD-ROMs,recordable CDs, rewritable CDs,

DVD-ROMs, BD-ROMs, HD DVD-ROMs, recordable DVDs, and

rewritable DVDs

Identify the uses of tapeIdentify the uses of tape

Discuss PC Cards, ExpressCard modules, and the various types of

miniature storage media

Discuss PC Cards, ExpressCard modules, and the various types of

miniature storage media

Identify uses of microfilm and microfiche

Identify uses of microfilm and microfiche

Next

Storage

What is storage? Holds data, instructions, and information for future use Storage medium is physical material used for storage

Also called secondary storage

Storage

What is capacity?

Kilobyte (KB) 1 thousand

Megabyte (MB) 1 million

Gigabyte (GB) 1 billion

Terabyte (TB) 1 trillion

Petabyte (PB) 1 quadrillion

Number of bytes (characters) a storage medium can hold

Exabyte (EB) 1 quintillion

Zettabyte (ZB) 1 sextillion

Yottabyte (YB) 1 septillion

Storage Medium(floppy disks, Zip disks,

hard disks, CDs)

Storage

How does volatility compare?

No

nvo

lati

le

Storage medium is nonvolatile—contents retained when power is off

Contents Contents retainedretained

Contents Contents available to useravailable to user

Memory(most RAM)

(chips on motherboard)

Screen Display

ON OFF

Vo

lati

le Display Display disappearsdisappears

Data andData andinstructions instructions

available to useravailable to user

Display Display appearsappears

Data and Data and instructions erasedinstructions erased

Memory is volatile—holds data and instructions temporarily

WritingWritingProcess of transferring Process of transferring

items from memory items from memory to storage mediato storage media

WritingWritingProcess of transferring Process of transferring

items from memory items from memory to storage mediato storage media

Storage

What is a storage device?

ReadingReadingProcess of transferring Process of transferring

items from storage items from storage media to memorymedia to memory

ReadingReadingProcess of transferring Process of transferring

items from storage items from storage media to memorymedia to memory

Hardware that Hardware that records and records and

retrieves items retrieves items to and from to and from

storage mediastorage media

Functions as source of input

Creates output

Floppy Disk Small files to be transported

Secondary Storage

Primary Storage

Hard Disk

Flash Memory Cards and USB Flash Drives

CDs and DVDs

Tape

Items waiting to be interpretedand executed by the processor

Operating system, applicationsoftware, user data and information

Digital pictures or files to be transported

Software, backups, movies, music

Backups

Memory (most RAM)

Stores …Transfer rates

Storage

What is access time? Time it takes storage device to locate item on storage medium Time required to deliver item from memory to processor

fastertransfer

rates

slowertransfer

rates

Magnetic Disks

What are tracks and sectors?

Formatting prepares disk for use

Trackis narrow

recording bandthat forms fullcircle on disk

Sector stores up to512 bytes

of data

Perpendicular recording

Magnetic Disks

What is a hard disk?hard disk mounted

in system unit

High-capacity storage Consists of several

inflexible, circular platters that store items electronically

Components enclosed in airtight, sealed case for protection

Longitudinal recording

Magnetic Disks

What are characteristics of a hard disk?

Sample Hard Disk Characteristics

Advertised capacity 500 GB

Platters 4

Read/write heads 8

Cylinders 16,383

Bytes per second 512

Sectors per track 63

Sectors per drive 973,773,168

Revolutions per minute 7,200

Transfer rate 300 MB per second

Access time 8.5 ms

actualdisk

capacity

Magnetic Disks

How does a hard disk work?

Step 1.Circuit board controls movement of head actuator and a small motor.

Step 2.Small motor spins platters while computer is running.

Step 3.When software requests a disk access, read/write heads determine current or new location of data.

Step 4.Head actuator positions read/write head arms over correct location on platters to read or write data.

Magnetic Disks

What is a cylinder? Vertical section of

track through all platters

Single movement of read/write head arms accesses all plattersin cylinder

platter

read/writehead

platter

sides

cylinder

track

sector

Magnetic Disks

What is a head crash?

Spinning creates cushion of air that floats read/write head above platter

Occurs when read/write head touches platter surface

A smoke particle, dust particle, or human hair could render drive unusable

Clearance between head and platter is approximately two-millionths of an inch

Magnetic Disks

What is a disk cache? Portion of

memory that processor uses to store frequently accessed items

second requestfor data—to hard disk

first requestfor data—to disk cache

Magnetic Disks

What is RAID? Redundant Array of Independent Disks Connects multiple smaller disks into a single unit that

acts as a single large hard disk

Magnetic Disks

What is a miniature hard disk? Provide greater storage capacities than flash memory Smaller than notebook computer hard disks A pocket hard drive is a self-contained unit

Magnetic Disks

What are external hard disks and removable hard disks?

External hard disk—freestandinghard disk that connects to system unit

Removable hard disk—hard diskthat you insert and removefrom hard disk drive

Used to back up or transfer files

SCSISCSIcontroller supports up to fifteencontroller supports up to fifteen

devices including hard disks, CDdevices including hard disks, CDand DVD drives, tape drives, printers,and DVD drives, tape drives, printers,

scanners, network cardsscanners, network cards

SATASATA (Serial Advanced Serial Advanced Technology AttachmentTechnology Attachment) controller ) controller

uses serial signals to transfer data, uses serial signals to transfer data, instructions, and informationinstructions, and information

Magnetic Disks

What is a disk controller?

EIDEEIDE (EEnhancednhanced IIntegratedntegrated DDrive rive EElectronics) controller supports four lectronics) controller supports four hard disks, provides connections for hard disks, provides connections for

CD and DVD drivesCD and DVD drives

Chip and circuits that Chip and circuits that control transfer of control transfer of items from diskitems from disk

Magnetic Disks

What is online storage?

Others can be authorized to access your data

Service on Web that provides storage for minimal monthly fee

Files can be accessed from any computer with Web access

Large files can be downloaded instantaneously

Magnetic Disks

What is a floppy disk? Portable, inexpensive storage

medium (also called diskette)

Thin, circular, flexible film enclosedin 3.5” wide plastic shell

Summary of Storage

Internal hard disksInternal hard disks

External and removable hard disksExternal and removable hard disks

Floppy disksFloppy disks

CD-ROMsCD-ROMs

Recordable and Rewritable CDsRecordable and Rewritable CDs

DVD-ROMsDVD-ROMs

Blu-ray Discs (BDs)Blu-ray Discs (BDs)

HD DVD discsHD DVD discs

Recordable and Rewritable DVDsRecordable and Rewritable DVDs

TapeTape

PC Cards and ExpressCard modules

PC Cards and ExpressCard modules

Flash memory cards and USB flash drives

Flash memory cards and USB flash drives

Storage Complete

Smart cards, microfilm, and microfiche

Smart cards, microfilm, and microfiche