1. Chapter 7 Storage

2. Arithmetic Logic Unit (ALU)
Ch 1 – Introduction
Ch 2 – Internet & WWW
Ch 3 – Application Software
Ch 8 – System Software
Ch 4
Processor
Control Unit
Arithmetic Logic Unit (ALU)
Control Unit
Arithmetic Logic Unit (ALU)
Instructions Data
Information
Memory
Input Devices
Ch 5
Information
Output Devices
Ch 6
Data
Instructions
Instructions Data Information
Storage Devices
Ch 7

4. What a storage device does?
Hardware that
writes
records to the medium
holds
them and
reads from
Reading
Transfers items from storage media to memory
Writing
Transfers items from memory to storage media

5. Reading is the process of transferring items from a storage medium into memory
Writing is the process of transferring items from memory to a storage medium

6. Physical material on which a computer keeps info
Storage device and a storage medium
storage device
Hardware that records, holds and retrieves items to and from a storage medium
storage medium
Physical material on which a computer keeps info

7. How does storage differ from memory?
Stores items for future use, rather than current use
Stores for a
long time, rather than temporarily
Storage is
nonvolatile, rather than volatile
To work with a file, you read a part (a block of records) from storage (block by block) and place it in memory
When you are finished with the block of a file, you write it from memory to the storage

8. How does volatility compare?
Contents of storage retained when power is off - nonvolatile
Screen display and contents of RAM are volatile –
erased when power is off

9. What is capacity? Number of bytes storage
medium can hold
Storage Term
Number of bytes
Kilobyte
Megabyte
Gigabyte
Terabyte
Petabyte KB MB TB GB PB
1 thousand
1 million
1 billion
1 trillion
1 quadrillion
Abbreviation

10. Google believes that the “plummeting price of storage” will allow iPods of the future (2020 A.D. ) to hold “any video ever produced”.
Greet class

12. Access time:
The amount of time it takes a storage device to locate an item on a storage medium

13. What is access time? cost speed
Memory (RAM)
Flash memory
Compact disk
Tape
Hard Disk
cost
less expensive
more expensive
speed
faster
slower
Amount of time it takes device to locate block on disk – measured in millisec /
microsec /
nanosec / picosec

14. Flash Memory Cards and USB Flash Drives
What is transfer rate?
Time required to deliver a block from storage to memory
in kilobytes/sec (KB/sec) or megabytes/sec (MB/sec)
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 interpreted and executed by the processor
Operating system, application software, user data and information
Digital pictures or files to be transported
Software, backups, movies, music
Backups
Memory (most RAM)
faster transfer rates
slower transfer rates

15. Hard disk contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information

17. Revolutions per Minute
Characteristics of a hard disk:
Capacity
Platters
Read/Write Heads
Cylinders
Sectors and Tracks
Revolutions per Minute
Transfer Rate
Access Time

18. Sample: Hard Disk Characteristics
Advertised capacity 500 GB
Platters 4
Read/write heads 8
Cylinders 16,383
Bytes per sector 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

19. Calculating capacity of a hard drive
Sector stores 512 bytes of data
16383 cylinders times 8 tracks in a cylinder times
63 sectors per track times 512 bytes per sector = 500 GB

22. An external hard disk is a separate free-standing hard disk that connects to your computer with a cable or wirelessly
A removable hard disk is a hard disk that you insert and remove from a drive
Internal and external hard disks are available in miniature sizes (miniature hard disks)

23. Track
Track
Arm
Head
Sector
Platter
Cylinder
Hard Disk Terminology

24. platter
track
sector
read/write head
platter
sides
cylinder

26. Cylinder is the collection of single tracks through all platters
Track is the narrow recording band that forms full circle on disk surface
Cylinder is the collection of single tracks through all platters
Single movement of read/write head arms can read any track on the cylinder
cylinder
track

27. What is a head crash?
Occurs when read/write head touches platter surface
Spinning creates cushion of air that floats read/write head above platter
A smoke particle, dust particle, or human hair could render drive unusable

28. How does RAID work? Redundant Array of Independent Disks
Disk system that duplicates data, instructions, and information to improve data reliability
Mirroring has one backup disk for each primary disk
mirroring (RAID Level 1)

29. External hard disk—freestanding hard disk that connects to system unit
Removable hard disk— you insert and remove from hard disk drive

30. What is a disk cache?
Portion of memory that processor uses to store frequently accessed items
first request for data goes to disk cache
second request for data goes to hard disk

31. Disk History
1973:
140 MB
1979:
2,300 Mbytes = 2.3 GB

32. 1 inch disk drive! Hitachi 2007 release
Development driven by iPods & digital cameras
20GB, 5-10MB/s

33. Generate less heat and consume less power
Flash Memory Storage
Flash memory chips contain no moving parts – solid state drives; they have several advantages over magnetic hard disks:
Faster access time
Faster transfer rates
Generate less heat and consume less power
Last longer

34. USB flash drives plug into a USB port on a computer or mobile device

36. Secure Digital High Capacity (SDHC)
A memory card is a removable flash memory that you insert and remove from a slot in a computer
CompactFlash (CF)
Secure Digital (SD)
Secure Digital High Capacity (SDHC)
microSD
microSDHC
xD Picture Card
Memory Stick
Memory Stick Micro (M2)

38. What are PC Cards? Add capabilities to computer
Credit-card-sized device commonly used in notebook computers

39. What is a smart card?
Stores data on microprocessor embedded in small card
Input, process, output, and storage capabilities

40. Cloud Storage

41. What are advantages of an Internet storage?
Accessibility
Files can be accessed from any computer or device with Web access
When in need
Large audio, video, and graphics files can be downloaded to an Internet hard drive
Share
Others can be authorized to access data from your Internet hard drive
Security
Allows offsite backups of data

42. Reasons to subscribe to cloud storage:
Access files from any computer
Store large files
Allow others to access their files
View data and images
Store offsite backups
Provide data center functions

43. What are optical discs?
Push the button to slide out the tray.
Flat, round, portable discs made of metal or plastic
Can be read only or read/write
Insert the disc, label side up.
Most PCs include an optical disc drive
Push the same button to close the tray.

44. How does a laser read data on an optical disc?
laser diode
prism
light- sensing diode 1
lens
pit
land
disc label
Step 3. Reflected light sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0.
Step 2. If light strikes a pit, it scatters. If light strikes a land, it is reflected back toward diode.
Step 1. Laser diode shines a light beam toward disc.

45. How is data stored on an optical disc?
Data is stored in single track
Track divided into evenly sized sectors that store items
single track spirals to edge of disc
disc sectors

46. How should you care for an optical disc?

47. X is 150 KBps (KB per second)
What is the data transfer rate of a CD drive?
75X
75  150 KBps = 11,250 KBps or MBps
Ranges from 48X to 75X
X is 150 KBps (KB per second)
48X: 48  150 KBps = 7,200 KBps or 7.2 MBps

48. A CD-ROM can be read from but not written to
A CD-R is an optical disc on which users can write, but not erase
A CD-RW is an erasable disc

49. What is a CD-ROM? Compact disc read-only memory
Cannot erase or modify contents
Typically holds 650 MB to 1 GB
Commonly used to distribute multimedia and software

50. What are CD-Rs and CD-RWs?
Must have CD recorder or CD-R drive
CD-R (compact disc-recordable)
you can write on once
Cannot erase disc’s contents
CD-RW (compact disc-rewritable)
disc you can write on multiple times
Must have CD-RW software and CD-RW drive

51. What is a DVD-ROM (digital video disc-ROM)?
Must have DVD-ROM drive or DVD player to read DVD-ROM
Stores databases, music, complex software, and movies
Blu-Ray discs have storage capacity of up to 100 GB
HD-DVD discs have storage capacity of up to 60 GB

52. Other Types of Storage Magnetic stripe cards and smart cards Tape
Microfilm and microfiche
Enterprise storage

53. What is a tape?
Magnetically coated plastic ribbon capable of storing large amounts of data at low cost
Used for backup

54. What is sequential access versus direct access?
Reading and writing data consecutively
Method used for tape
direct access
You can locate a particular data item or file immediately
Method used for hard disks, and compact discs
Also called random access

55. How is data stored on a tape?
Sequential access
Reads and writes data consecutively, like music tape
Unlike direct access ( used on hard disks, CDs, and DVDs ) which can locate particular item much faster

56. A magnetic stripe card A smart card
contains a magnetic stripe that stores information
A smart card
stores data on a microprocessor embedded in the card

57. Microfilm and Microfiche
Store microscopic images of documents on roll or sheet of film
Images are recorded using computer output microfilm recorder
Microfilm — 100- to 215-foot roll of film
Microfiche — small sheet of film, usually 4”  6”

59. Enterprise storage stores huge volumes of data and information for large businesses
Uses special hardware for heavy use, maximum availability, and maximum efficiency

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