1 intro to info tech storage devices copyright 2003 by janson industries this presentation can be...

1

Intro to Info TechStorage Devices

Copyright 2003 by Janson Industries

This presentation can be viewed on line at: http://web.fscj.edu/Janson/cgs1060/wk08.Storage.ppt

Copyright 2012 by Janson Industries2

Objectives

Explain the various devices

Explain and compare the relative advantages and disadvantages


Storage Devices Hold data and instructions, can also

hold output

Comprised of a device and media Device writes to and reads from a

particular medium

Been around since beginning of computers

Early medium – punch cards


Storage Devices Measured two ways

Speed (access/write/rewrite)

Capacity

Also, compared according to

Portability – can medium be moved to another device

"Rewritability" – once written to can medium be it be changed


Storage Devices

Secondary storage vs. Internal storage (Main Memory/MM)

Slower access SS measured in microseconds, PC

MM nanoseconds

Holds much more PC MM measured in GB, SS TB


Storage Device Types Magnetic Disks

Optical Disks

Other


Magnetic Disks Surface can be magnetized and

demagnetized

Magnetic state represents a 0 or 1

Surface broken up into

Tracks

Pie shaped sections

Sectors Tracks and sections numbered This provides identifier for sectors


Magnetic Disks 2 types

Floppy disk/floppy drive Portable media

Hard disk/hard drive Some are/some are not portable Most desktop PCs have a single unit

where medium can't be separated and moved to another device


Floppy Disks Historically, different sizes

3.5, 5.25, 8

3.5 holds about 1.44 megs

Single vs. double sided

Zip disks hold a lot more


Hard Disk Made up of multiple inflexible

platters

Read/write heads One for each platter surface

How heads and platter work: Heads 2 millionths of an inch over

surface Sense the magnetic state of

platter surface Head crash – Bad!


Hard Disk How the whole thing works

Arm extended to correct track

Platter spun so correct sector is under read/write head

Surface read and value sent via circuitry through the arm

http://www.youtube.com/watch?v=9eMWG3fwiEU


Hard Disk With hard disks, different units of

storage Cluster: group of adjacent sectors,

smallest unit of allocatable storage Cylinder: all same tracks on different

platter surfaces

To make access faster try to store info In one track If data larger than a track, store in same

cylinder Why?


Other Hard Disks External hard disks

One unit separate from system unit Plugs into USB port Capacity in TBs Some more portable than others

Removable HD Very portable Machines must have a removable

HD bay


Other Hard Disks Miniature HDs

Often built into a mobile device like camera, headphones

Pocket HD has more capacity than a thumb

Large systems have many hard drives Will have disk controller(s)

Specialized chip that manages communication with disk drives

Decreases work for the CPU


Optical Disks Surface of the disk is altered to

affect it's reflectivity

To read, a beam of light is shot onto the surface

The amount of light reflected will represent a 0 or 1


Optical Disks Compared by their

Sidedness Capacity Speed Read/Write capability

Reading is called ripping Writing is called burning

2 major types CDs DVDs


Compact Discs Usually

One sided

Capacity 650MB – 1GB

Different types determined by the read/write capability CD-ROM

CD-R

CD-RW


Compact Discs CD-ROM (Read Only Memory)

Single session – can write to disc once

Can read many times

Used to be called a WORM disc

What good is this type of CD? S/W mfgs write to these type of disks

and then distribute

Users can't inadvertently erase the application


Compact Discs CD-R (Read)

Multi-session – can write to one portion of disk and then later to another

Can read many times

Can't erase what is written

CD-RW (Rewritable) Can write, read, erase, and rewrite to

disc


CD Drives Compared by

The type of discs they support Can they read and/or write

Read, write, rewrite speed

Measured like this: Read 128X Write 64X Rewrite 24X


DVDs Digital Versatile Disc

Holds more than CDs 4.7GB to 100GB

Capacity depends on whether Single or double sided Regular or high capacity DVD Single or multiple layers

Battle for high capacity DVD format between Blu-ray and HD Blu-ray won! (BD)


Reading and Writing to DVDs For Blu-ray, two types of discs

BD-R is read only BD-RE can read and write

Regular discs are more complicated DVD+R and DVD-R are read only DVD+RW, DVD-RW, and DVD+RAM

can read and write

The DVD drive must support the particular DVD format Most DVD drives support CDs


Reading and Writing to DVDs DVD-R approved by DVD Forum

Mitsubishi, Sony, Hitachi, and Time Warner

DVD+R supported by the DVD+RW Alliance. Sony, Yamaha, Philips, Dell, and HP

Differences Defects management How DVDs are formatted and rewritten What TV DVD players will play them For computer backups, either one will do


Other Storage Tape

A magnetic ribbon

Two formats: Cartridge Reel to reel

Only provides sequential access Discs provide direct access

Tapes often used for back up


Other Storage Flash memory cards

Flash memory (i.e. chip based)

Used in notebooks, cameras, PDAs

Need a special drive/slot in device

USB Flash drives (aka Thumb drives)

Comprised of both media and device

Don't need special drive/slot, just need a USB port


Other Storage Smart cards

Chip based memory

Can also process information Holds a defined amount of money You buy something, that amount is

decreased

Online

Can access files from anywhere

Give others access

Many are free


Online Storage Three big players (as of 5/2012)

Google Drive 5 GB free, 100GB more $59.88

OneDrive -formerly Skydrive (MS) 15 GB free (7/14), 100GB more $50.00

Dropbox (Dropbox Inc.) 2 GB free, 100GB more $199.00


Online Storage Also compared based on

Search – can file content be basis Dropbox only scans file names

OneDrive supports content scan for MS formats (Word, Excel, PP, etc.)

Google supports many formats, even uses OCR for scanned content

Others access With Google Drive, file is either view or edit

OneDrive lets you specify for each file/user

Dropbox must set up a shared folder for edit


Other Storage Microfilm and Microfiche

Film is reel to reel, fiche is small rectangle of plastic film

Hold microscopic images Need separate devices to read and write Readers considered auxiliary devices not

peripheral devices Don't need the CPU to access the storage

medium Extremely long lasting 100-500 years

Magnetic disk 5-30 yrs Optical 10-100 yrs


Other Storage Enterprise storage - vast

amount of capacity

Storage array Separate device comprised of

hundreds of disks Have multiple processors Act as "storage servers" Capacities up to .5 PB (half a

quadrillion bytes)


Other Storage Solid state hard drive (SSD)

Uses non-volatile memory chips No moving parts Much faster than magnetic disk (up

to 100X) More expensive (up to 20X) Limited number of writes (1-5 mill)

Often used in combination with magnetic disk SSD acts as cache for frequently

used files


Points to Remember Secondary storage: non-volatile storage

managed by a dedicated storage device

Secondary storage serves as a source of input and target for output

Wide variety of media measured by Speed Capacity Durability Read/write capability

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