Chapter 7 Objectives - University of Minnesota Duluth

1 1 Chapter 7 StorageDifferentiate betweenstorage and memoryIdentify various types of storage media and storage devices Explain how a floppy disk stores dataIdentify the advantages of using high-capacity disksDescribe how a hard disk organizes dataIdentify the advantages of using an Internet hard driveExplain how a compact disc stores dataUnderstand how to care fora compact discDifferentiate between CD-ROMs, CD-RWs, DVD-ROMs and DVD+RWsIdentify the uses of tapeUnderstand how an enterprise storage system worksExplain how to use PC Cards and other miniaturestorage mediaIdentify uses of microfilmand microficheChapter 7 Objectivesp. 7. 2 Fig. 7-1 Memory Versus StorageWhat is storage ? Media and devices used to store and retrieve data, instructions, and informationNextp.

2 7. 4 Memory Versus StorageHow does storagediffer from memory?When you want to work with a file, you read it from storage and place it in memoryWhen you are finished with the file, you write it from memory into storage Stores items for future use, rather than temporarily storage is nonvolatile, rather than volatileNextMemory Versus StorageHow does volatilitycompare?p. 7. 4 Fig. 7-2 Contents of storage retained when power is offContents of storage retained when power is offScreen display and contents of most RAM (memory) erased when power is offScreen display and contents of most RAM (memory) erased when power is offNextp. 7. 4 Memory Versus StorageWhat is a storage deviceand a storagemedium? storage mediumPhysical material on which a computer keeps data, instructions, and informationstorage deviceHardware that records and retrieves items to and from a storage mediumNext2p.

3 7. 4 Memory Versus StorageWhat is readingand writing?readingProcess of transferring data, instructions, and information from a storage medium into memoryServes as a sourceof inputNextwritingProcess of transferring items from memory to a storage mediumServes as a source of outputp. Fig. 7-4 Memory Versus StorageMemory (RAM)Compact DiscFloppy DiskTapeHard Diskcostless expensivemore expensivespeedfasterslowerNextWhat is access time? Amount of time it takes device to locate item on disk Defines speed of disk storagedevicep. 7. 5 Fig. 7-3 Memory Versus StorageWhat is capacity? Numberof bytes (characters) storage medium can holdNextStorage TermNumber of bytesKilobyteMegabyteGigabyteTerabytePet abyteKBMBTBGBPB1 thousand1 million1 billion1 trillion1 quadrillionAbbreviationp.

4 7. 6 Floppy DisksWhat is a floppy disk? Portable, inexpensive storage medium Today s standard disk is wideNextp. Fig. 7-5 Floppy DisksWhat are the parts of a floppy disk? Thin, circular, flexible film enclosed between two linersshellshutterlinermagnetic coatingflexible thin filmmetal hubNextp. 7. 6 Floppy DisksHow are floppy disk drives designated?Two floppy drivesdrive Adrive BOne floppy drivedrive ANext36: Read/write heads read data from or write data on the floppy diskStep 65: Motor positions read/write heads over correct location on diskStep 54: Motor causes floppy disk to spinStep 43: If write instruction, circuit board verifies whether disk can be written toStep 32: Signal sent to control movement of read/write heads and diskStep 21: Shutter moves to expose recording surface on diskStep 1p.

5 7. 7 Fig. 7-7 Floppy DisksHow does a floppy disk drive work?Nextp. Fig. 7-8 Floppy DisksWhat are tracksand sectors? Track is narrow recording band that forms full circle on disk surface Sector can store up to 512 bytes of dataNextsector18 per tracktrack80 per side80 tracks per side X 18 sectors per track X 2 sides per disk X 512 bytes per sector = 1,474,560 bytesp. 7. 8 Fig. 7-9 Floppy DisksWhat is formatting?Next Process of preparing disk for reading and writing Formatting marks bad sectors as unusablep. DisksHow do you care for a floppy? Proper care helps maximize disk s life Floppy disk can last at least seven yearsNextAvoid exposure to heat and coldAvoid exposure to magnetic fieldsAvoid exposure to contaminants such as dust, smoke, or salt airKeep disks in a storage tray when not using themNever open the shutter and touch the disk s recording surfacewrite-protectednot write-protectedp.

6 7. 9 Fig. 7-10 Floppy Disks Small opening with a cover that you slide Protects floppy disks from being erased accidentallyNextnotch closed means you can write on the disknotch closed means you can write on the disknotch open means you cannot write on the disknotch open means you cannot write on the diskWhat is a write-protect notch?p. Fig. 7-11 High-Capacity DisksWhat is a high-capacity disk drive? Uses disks with capacities of 100 MB and greater Primarily used to backup files and transfer filesNextZip driveUses a Zip disk that can store 100 MB or 250 MB of databuilt in Zip drive4p. DisksWhat is a backup? Duplicate of file, program, or disk that you can use if original is lost, damaged, or destroyedNextdatainstructionsinformation p.

7 7. 10 Fig. 7-12 Hard DisksWhat is a hard disk? High-capacity storage Consists of several inflexible, circular platters that store items electronically Components enclosed in airtight, sealed case for protectionNexthard disk installed in system unit4: Head actuator positions read/write head arms over correct location on platters to read or write dataStep 42: Small motor spins plattersStep 23: When software requests disk access, read/write heads determine location of dataStep 31: Circuit board controls movement of head activator and small motorStep 1p. Fig. 7-13 Hard DisksHow does a hard disk work?Nextp. 7. 11 Fig. 7-14 Hard DisksWhat is a cylinder? Location of a single track through all platters Single movement of read/write head arms can read same track on all plattersNexttrackcylinderp.

8 7. 12 Fig. 7-15 Hard DisksWhat is a head crash? Occurs when read/write head touches platter surface Spinning creates cushion of air that floats read/write head above platterNexthairread/write headdustsmokeplattergapclearance between head and platter is approximately two millionths of an inchclearance between head and platter is approximately two millionths of an inchgap is half the diameter of a dust particlegap is half the diameter of a dust particleprocessorhard diskdisk cacheprocessorhard diskdisk cachefirst request for data to disk cachep. 7. 12 Fig. 7-16 Hard DisksWhat is a disk cache? Portion of memory processor uses to store frequently accessed itemsNextprocessorhard diskdisk cachesecond request for data to hard diskfirst request for data to disk cache5p.

9 7. 12 Hard DisksWhat is a partition? Formatted hard disk divided into separate areas called partitions Each partition functions as if it were a separate hard disk driveNextdrive CDesignation for first partition or for a single partition on hard diskdrive DDesignation for second partition on hard diskone hard disk divided into two partitionsp. 7. 13 Fig. 7-17 Hard DisksWhat is a removable hard disk? Disk drive in which a plastic or metal case surrounds the hard disk so you can remove it from the drive Used for backup or to transfer filesNextPeerless stores up to 20 GBJaz stores up to 2 GBp. 7. 14 Fig. 7-19 Hard DisksHow does RAID work? Disk system that duplicates data, instructions, and information to improve data reliabilityNextmirroring(RAID Level 1)striping Mirroringhas one backup disk for each disk Stripingstores data across multiple disksp.

10 7. 15 Fig. 7-20 Hard DisksNextWhat Windowsutilities maintain a hard disk drive?System Toolsp. 7. 16 Fig. 7-21 Hard DisksWhat is an Internet hard drive? Service on Web that provides storage to computer users Most offerfree storage Revenues come from offsite backups of dataOthers can be authorized to access data from your Internet hard driveFiles can be accessed from any computer or device with Web accessLarge audio, video, and graphics files can be downloaded to an Internet hard drive instantaneouslyp. 7. 16 Hard DisksWhat are advantages of an Internet hard drive?Next6p. 7. 17 Compact DiscsWhat is a compact disc (CD)?Next storage medium Most PCs include some type of compact disc drive Available invariety offormatsCD-ROMCD-RCD-RWDVD-ROMDVD+RWp.