Presentation Transcript

1. Chapter 7Storage

2. Ch 4 Processor Control Unit Arithmetic Logic Unit (ALU) InstructionsDataInformation InstructionsData Information Ch 1 – Introduction Ch 2 – Internet & WWW Ch 3 – Application Software Ch 8 – System Software Control Unit Arithmetic Logic Unit (ALU) Memory InputDevices Ch 5 OutputDevices Ch 6 Information Data Instructions Storage Devices Ch 7
3. What astorage 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
4. 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
5. 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 When you are finished with the block of a file, you write it from memory to the storage To work with a file, you read a part (a block of records) from storage (block by block) and place it in memory
6. Contents of storage retained when power is off - nonvolatile Screen display and contents of RAM are volatile – erased when power is off How does volatility compare?
7. What is capacity? Number of bytes storage medium can hold Storage Term Number of bytes Abbreviation KB 1 thousand Kilobyte MB 1 million Megabyte 1 billion GB Gigabyte 1 trillion TB Terabyte PB 1 quadrillion Petabyte
8. Google believes that the“plummeting price of storage” will allow iPods of the future (2020 A.D. ) to hold “any video ever produced”.
9. Access time: The amount of time it takes a storage device to locate an item on a storage medium
10. What is access time? Amount of time it takes device to locate block on disk – measured in millisec / microsec / nanosec / picosec Memory (RAM) faster more expensive Hard Disk cost speed Flash memory slower less expensive Compact disk Tape
11. Primary Storage Memory (most RAM) Items waiting to be interpretedand executed by the processor Secondary Storage Hard Disk Operating system, applicationsoftware, user data and information Flash Memory Cards and USB Flash Drives Digital pictures or files to be transported CDs and DVDs Software, backups, movies, music Tape Backups Floppy Disk Small files to be transported Time required to deliver a block from storage to memory in kilobytes/sec (KB/sec) or megabytes/sec (MB/sec) What istransfer rate? fastertransferrates slowertransferrates
12. Hard diskcontains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information
13. Characteristics of a hard disk:
14. 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
15. 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 times512 bytes per sector = 500 GB
16. Hard Disk Terminology Sector Track Track Arm Head Platter Cylinder
17. platter track sector read/writehead platter sides cylinder
18. 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
19. Occurs when read/write head touches platter surface What is ahead crash? Spinning creates cushion of air that floats read/write head above platter A smoke particle, dust particle, or human hair could render drive unusable
20. How does RAID work? Redundant Array of Independent Disks Disk system that duplicates data, instructions, and information to improve data reliability mirroring(RAID Level 1) Mirroring has one backup disk for each primary disk
21. External hard disk—freestandinghard disk that connects to system unit Removable hard disk— you insert and removefrom hard disk drive
22. first requestfor data goes to disk cache second requestfor data goes to hard disk Portion of memory that processor uses to store frequently accessed items What is adisk cache?
23. Disk History 1973: 140 MB 1979: 2,300 Mbytes = 2.3 GB
24. 1 inch disk drive! Hitachi 2007 release Development driven by iPods & digital cameras 20GB, 5-10MB/s
25. Flash Memory Storage Flash memory chips contain no moving parts – solid state drives; they have several advantages over magnetic hard disks:
26. USB flash drivesplug into a USB port on a computer or mobile device
27. A memory cardis a removable flash memory that you insert and remove from a slot in a computer
28. What arePC Cards? Add capabilities to computer Credit-card-sized device commonly used in notebook computers
29. What is asmart card? Stores data on microprocessor embedded in small card Input, process, output, and storage capabilities
30. Cloud Storage
31. What are advantages of an Internet storage? When in need Large audio, video, and graphics files can be downloaded to an Internet hard drive Accessibility Files can be accessed from any computer or device with Web access Share Others can be authorized to access data from your Internet hard drive Security Allows offsite backups of data
32. Reasons to subscribe to cloud storage:
33. What areoptical discs? Push the button toslide 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 buttonto close the tray.
34. disc label lens lens pit land 0 1 prism prism light-sensingdiode light-sensingdiode laserdiode laserdiode How does a laser read data on an optical disc? 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 strikesa pit, it scatters. If light strikes a land, it is reflected back toward diode. Step 1.Laser diode shines a light beam towarddisc.
35. Data is stored in singletrack How is data stored on an optical disc? Track divided into evenly sizedsectorsthat store items single trackspirals to edgeof disc disc sectors
36. How should you care for an optical disc?
37. What is the data transfer rate of a CD drive? 75X 75  150 KBps = 11,250 KBpsor 12.25 MBps Ranges from 48X to 75X X is 150 KBps(KB per second) 48X: 48  150 KBps = 7,200 KBpsor 7.2 MBps
38. Compactdiscread-onlymemory What is aCD-ROM? Cannot erase or modify contents Typically holds 650 MB to 1 GB Commonly used to distribute multimedia and software
39. Must haveCD recorderor CD-R drive What areCD-Rs and CD-RWs? CD-R (compact disc-recordable) you can write on once Cannot erasedisc’s contents CD-RW (compact disc-rewritable) disc you can write onmultiple times Must haveCD-RW softwareand CD-RW drive
40. Must haveDVD-ROM driveor 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 What is aDVD-ROM(digital video disc-ROM)?
41. Other Types of Storage
42. What isa tape? Magnetically coated plastic ribboncapable of storing large amountsof data at low cost Used for backup
43. What is sequential access versus direct access? sequential 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
44. Sequential access How is data stored on a tape? 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
45. A magnetic stripe card contains a magnetic stripe that stores information A smart card stores data on a microprocessor embedded in the card
46. Microfilm and Microfiche Microfilm — 100- to215-foot roll of film Microfiche — small sheet of film, usually 4”  6” Store microscopic images of documents on roll or sheet of film Images are recorded using computer output microfilm recorder
47. 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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