Chapter 7, Storage
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Chapter 7 Objectives Explain how a compact disc Differentiate between stores data storage and memory Understand how to care for Identify various types of storage a compact disc media and storage devices Differentiate between CD-ROMs, CD-RWs, DVD-ROMs and Chapter 7 Explain how a floppy disk DVD+RWs stores data Storage Identify the uses of tape Identify the advantages of using high-capacity disks Understand how an enterprise storage system works Describe how a hard disk Explain how to use PC Cards organizes data and other miniature storage media Next Identify the advantages of using an Internet hard drive Identify uses of microfilm p. 7.2 and microfiche Memory Versus Memory Versus Storage Storage What is storage? How does • Media and devices used to store and storage differ retrieve data, instructions, and from memory? information • Stores items for When you want to work When you are future use, with a file, finished with rather than you read it the file, you from storage write it from temporarily and place it in memory into • Storage is memory storage nonvolatile, rather than volatile Next Next p. 7. 2 Fig. 7-1 p. 7. 4 Memory Versus Memory Versus Storage Storage How does volatility compare? What is a storage device and a storage medium? storage device Hardware that records ContentsContents of of storage and retrieves items to storage and from a storage retainedretained when when medium powerpower is is off off storage medium Physical material on which a computer Next Next keeps data, ScreenScreen display display and and contents contents instructions, and p. 7. 4 Fig. 7-2 ofof most most RAM RAM (memory) (memory) p. 7. 4 erasederased when when power power is is off off information 1 Memory Versus Memory Versus Storage Storage What is reading What is access time? and writing? e • Amount of time v i f s a n s Memory t it takes device e e p r reading x (RAM) e to locate item e r Process of transferring o on disk m data, instructions, Hard Disk and information from a storage medium writing • Defines speed cost speed into memory Process of of disk storage Compact Disc Serves as a source transferring items device e s v i lo of input from memory to a s w n e e r storage medium p x e Floppy Disk Serves as a s s e source of output l Next Next p. 7. 4 p. 7.4 Fig. 7-4 Tape Memory Versus Floppy Disks Storage What is capacity? What is a floppy disk? • Number Storage Abbreviation Number • Portable, of bytes Term of bytes inexpensive (characters) storage storage Kilobyte KB 1 thousand medium medium can Megabyte MB 1 million hold • Today’s Gigabyte GB 1 billion standard disk is 3.5” wide Terabyte TB 1 trillion Petabyte PB 1 quadrillion Next Next p. 7. 5 Fig. 7-3 p. 7. 6 Floppy Disks Floppy Disks What are the parts of a floppy disk? How are floppy disk drives designated? • Thin, circular, flexible film liner One floppy drive enclosed drive A between two shutter liners Two floppy metal drives hub drive A drive B Next magnetic Next p. 7.6 Fig. 7-5 shell flexible p. 7. 6 coating thin film 2 Floppy Disks How does a floppy disk drive work? Floppy Disks 1: Shutter moves to 2: Signal sent to control 3: If write instruction, circuit What are tracks and sectors? expose recording movement of read/write board verifies whether disk can surface on disk heads and disk be written to • Track is sector 18 per track 4: Motor causes Step 2 narrow track floppy disk to spin Step 1 recording 80 per side 5: Motor positions Step 6 band that read/write heads forms full over correct circle on disk location on disk surface 6: Read/write • Sector can heads read data Step 5 store up to from or write data on the floppy disk Step 4 512 bytes of Step 3 data Next Next p. 7. 7 Fig. 7-7 p. 7.8 Fig. 7-8 80 tracks per side X 18 sectors per track X 2 sides per disk X 512 bytes per sector = 1,474,560 bytes Floppy Disks Floppy Disks What is formatting? How do you care for a floppy? • Process of preparing disk for • Proper care helps reading and writing maximize disk’s Avoid exposure • Formatting marks bad sectors life Avoid exposure to heat and cold to magnetic as unusable • Floppy disk can fields last at least seven years Avoid exposure to contaminants such as dust, smoke, or salt air Never open the shutter and touch the disk’s recording Keep disks in a surface storage tray Next Next when not using p. 7. 8 Fig. 7-9 p. 7.9 them Floppy Disks High-Capacity Disks What is a What is a high-capacity disk drive? write-protect notchnotch open open • Uses disks with capacities of notch? meansmeans you you 100 MB and greater cannotcannot write write write-protected on the disk • Small opening on the disk • Primarily used to backup files with a cover and transfer files notch closed not write-protected that you slide notch closed meansmeans you you • Protects floppy cancan write write on on disks from thethe disk disk being erased ® ® accidentally Zip drive built in Zip drive Uses a Zip® disk that can store 100 MB or 250 MB of Next Next data p. 7. 9 Fig. 7-10 p. 7.9 Fig. 7-11 3 High-Capacity Disks Hard Disks What is a backup? What is a hard disk? • Duplicate of file, • High-capacity program, or disk that storage you can use if original is • Consists of lost, damaged, or several inflexible, in s circular platters destroyed t ru c that store items t io n electronically s • Components ta in a fo d enclosed in rm a airtight, sealed tio Next n Next hard disk case for p. 7.9 p. 7. 10 Fig. 7-12 installed in system unit protection Hard Disks Hard Disks cylinder track 3: When software How does a hard disk work? requests disk What is a cylinder? access, read/write 1: Circuit board controls 2: Small motor heads determine • Location of a single movement of head spins platters location of data activator and small motor track through all platters Step 2 4: Head actuator Step 1 • Single movement of positions read/write head read/write head arms arms over correct can read same track location on platters to read or on all platters write data Next Step 3 Next p. 7.11 Fig. 7-13 Step 4 p. 7. 11 Fig. 7-14 Hard Disks Hard Disks What is a head crash? What is a disk cache? • Occurs when read/write head touches platter • Portion of surface memory • Spinning creates cushion of air that floats read/write processor head above platter gapgap is is half half the the uses to processor diameterdiameter of of a a dustdust particle particle store clearanceclearance disk cache between head frequently between head hard disk andand platter platter is is hair accessed approximatelyapproximately items twotwo millionths millionths read/write head ofof an an inch inch dust first request for data — Next smoke Next to disk cache gap p. 7. 12 Fig. 7-15 p. 7. 12 Fig. 7-16 platter second request for data — to hard disk 4 Hard Disks Hard Disks What is a partition? What is a removable hard disk? • Formatted hard • Disk drive in which a plastic or metal case disk divided into drive C surrounds the hard disk so you can remove it from separate areas Designation for first the drive partition or for a single called partitions partition on hard disk • Used for backup or to transfer files • Each partition functions as if it were a separate one hard disk Peerless hard disk drive divided into stores up two partitions drive D Designation for second to 20 GB partition on hard disk Next Next Jaz stores p. 7. 12 p. 7. 13 Fig. 7-17 up to 2 GB Hard Disks Hard Disks How does RAID work? What Windows • Disk system that duplicates data, instructions, and utilities information to improve data reliability maintain a hard Mirroring has one backup disk for each disk disk drive? Striping stores data across multiple disks mirroring (RAID Level 1) striping Next Next p. 7. 14 Fig. 7-19 p. 7. 15 Fig. 7-20 System Tools Hard Disks Hard Disks What is an Internet hard drive? driveway.com What are advantages of an Internet hard drive? • Service on Web that provides storage to Large audio, video, and graphics files can computer users be downloaded to an Files can be • Most offer Internet hard drive accessed from any instantaneously computer or device free storage with Web access • Revenues come from Others can be advertisers authorized to access Allows offsite data from your Internet backups of data hard drive Next Next p. 7. 16 Fig. 7-21 p. 7. 16 5 Compact Discs Compact Discs M What is a compact disc (CD)? RO How do you use a compact disc? D- InsertInsert disc, disc, • Storage medium • CD drives can label side up C C PushPush button button label side up D to slide out • Most PCs include -R read compact to slide out W CD thethe tray tray some type of compact -R discs, including disc drive audio discs • Available in +RW variety of DVD formats PushPush the the same same Next OM Next buttonbutton to to close close p. 7. 17 -R p.