1. Intro to Info Tech Storage Devices
1/12/2018
Intro to Info Tech
Storage Devices
This presentation can be viewed on line at:
Copyright 2003 by Janson Industries

2. Objectives Explain the various devices
1/12/2018
Objectives
Explain the various devices
Explain and compare the relative advantages and disadvantages

3. Storage Devices Hold data and instructions, can also hold output
1/12/2018
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

4. Storage Devices Measured two ways Also, compared according to
1/12/2018
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

5. 1/12/2018
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

6. 1/12/2018
Storage Device Types
Magnetic Disks
Optical Disks
Other

7. Magnetic Disks Surface can be magnetized and demagnetized
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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

8. Magnetic Disks 2 types Floppy disk/floppy drive Hard disk/hard drive
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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

9. Floppy Disks Historically, different sizes Single vs. double sided
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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

10. Hard Disk Made up of multiple inflexible platters Read/write heads
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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!

11. Hard Disk How the whole thing works
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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

12. Hard Disk With hard disks, different units of storage
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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?

13. Other Hard Disks External hard disks Removable HD
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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

14. Other Hard Disks Miniature HDs Large systems have many hard drives
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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

15. 1/12/2018
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

16. Optical Disks Compared by their 2 major types Sidedness Capacity Speed
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Optical Disks
Compared by their
Sidedness
Capacity
Speed
Read/Write capability
Reading is called ripping
Writing is called burning
2 major types
CDs
DVDs

17. 1/12/2018
Compact Discs
Usually
One sided
Capacity 650MB – 1GB
Different types determined by the read/write capability
CD-ROM
CD-R
CD-RW

18. Compact Discs CD-ROM (Read Only Memory) What good is this type of CD?
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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

19. Compact Discs CD-R (Read) CD-RW (Rewritable)
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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

20. CD Drives Compared by The type of discs they support
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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

21. DVDs Digital Versatile Disc Holds more than CDs
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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)

22. Reading and Writing to DVDs
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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

23. Reading and Writing to DVDs
1/12/2018
Reading and Writing to DVDs
DVD-R approved by DVD Forum
Includes: Mitsubishi, Sony, Philips, Hitachi, Time Warner and others
DVD+R supported by the DVD+RW Alliance.
Includes: Sony, Yamaha, Philips, Dell, HP and others
Differences
Defects management
How DVDs are formatted and rewritten
What TV DVD players will play them
For computer backups, either one will do

24. Other Storage Tape A magnetic ribbon Two formats:
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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

25. Other Storage Flash memory cards USB Flash drives (aka Thumb drives)
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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

26. Other Storage Smart cards Online Chip based memory
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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

27. Online Storage Three big players (8/2015)
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Online Storage
Three big players (8/2015)
Google Drive
15 GB free
OneDrive -formerly Skydrive (MS)
Dropbox (Dropbox Inc.)
2 GB free, 1 TB $7.99/month
All offer other ways to get more
Referals, buy a device, exempt music

28. Online Storage Also compared based on (as of 5/12)
1/12/2018
Online Storage
Also compared based on (as of 5/12)
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

29. Other Storage Microfilm and Microfiche
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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 years
Magnetic disk 5-30 yrs
Optical yrs

30. Other Storage Enterprise storage - vast amount of capacity
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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)

31. Other Storage Solid state hard drive (SSD)
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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

32. 1/12/2018
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