Chapter 5 Storage Devices - FTMS

1 CSCA0101 Computing Basics1 CSCA0101 COMPUTING BASICSC hapter 5 Storage DevicesCSCA0101 Computing Basics2 Storage Data of Device Examples of Storage DeviceCSCA0101 Computing Basics3 Storage DevicesStorage Devices Astoragedeviceisusedinthecomputerstostor ethedata. Computing Basics4 Storage DevicesTypesofStorageTherearefourtypeofs torage: Primary Storage Secondary Storage Tertiary Storage Off-line StorageCSCA0101 Computing Basics5 Storage DevicesPrimaryStorage Alsoknownasmainmemory. Mainmemoryisdirectlyorindirectlyconnecte dtothecentralprocessingunitviaamemorybus . TheCPUcontinuouslyreadsinstructionsstore dthereandexecutesthemasrequired. Example: RAM ROM CacheCSCA0101 Computing Basics6 Storage DevicesPrimaryStorageRAM ItiscalledRandomAccessMemorybecauseanyof thedatainRAMcanbeaccessedjustasfastasany oftheotherdata.

2 There are two types of RAM: DRAM (Dynamic Random Access Memory) SRAM (Static Random Access Memory)CSCA0101 Computing Basics7 Storage DevicesPrimaryStorageRAMS tatic RAMD ynamic RAM Faster More expensive More power consumption does not need to be refreshed Slower Less expensive Less power consumption needs to be refreshed thousands of times per secondCSCA0101 Computing Basics8 Storage DevicesPrimaryStorageROM Thismemoryisusedasthecomputerbeginstoboo tup. Smallprogramscalledfirmwareareoftenstore dinROMchipsonhardwaredevices(likeaBIOS chip),andtheycontaininstructionsthecompu tercanuseinperformingsomeofthemostbasico perationsrequiredtooperatehardwaredevice s. Computing Basics9 Storage DevicesPrimaryStorageCache Cacheisahigh-speedaccessareathatcanbeeit herareservedsectionofmainmemoryorastorag edevice. MostcomputerstodaycomewithL3cacheorL2cac he, Computing Basics10 Storage DevicesSecondaryStorage ItisnotdirectlyaccessiblebytheCPU.

3 Computerusuallyusesitsinput/outputchanne lstoaccesssecondarystorageandtransfersth edesireddatausingintermediateareainprima rystorage. Example: HarddiskCSCA0101 Computing Basics11 Storage DevicesSecondaryStorageHardDisk Theharddiskdriveisthemain,andusuallylarg est,datastoragedeviceinacomputer. Itcanstoreanywherefrom160gigabytesto2ter abytes. Harddiskspeedisthespeedatwhichcontentcan bereadandwrittenonaharddisk. Aharddiskunitcomeswithasetrotationspeedv aryingfrom4500to7200rpm. Computing Basics12 Storage DevicesSecondaryStorageHardDiskInternal Hard diskExternal Hard diskCSCA0101 Computing Basics13 Storage DevicesSecondaryStorageHardDiskInternal Hard diskExternal Hard diskPortabilityNoYesPriceLess expensiveMore expensiveSpeedFastSlowSizeBigSmallCSCA01 01 Computing Basics14 Storage DevicesTertiaryStorage Typicallyitinvolvesaroboticmechanismwhic hwillmount(insert)anddismountremovablema ssstoragemediaintoastoragedevice.

4 Itisacomprehensivecomputerstoragesystemt hatisusuallyveryslow,soitisusuallyusedto archivedatathatisnotaccessedfrequently. Thisisprimarilyusefulforextraordinarilyl argedatastores, Computing Basics15 Storage DevicesTertiaryStorage Examples: MagneticTape OpticalDiscCSCA0101 Computing Basics16 Storage DevicesTertiaryStorageMagneticTape Amagneticallycoatedstripofplasticonwhich datacanbeencoded. Tapesforcomputersaresimilartotapesusedto storemusic. Computing Basics17 Storage DevicesTertiaryStorageOpticalDisc Opticaldiscisanystoragemediathatholdscon tentindigitalformatandisreadusingalasera ssemblyisconsideredopticalmedia. Themostcommontypesofopticalmediaare Blu-ray(BD) CompactDisc(CD) DigitalVersatileDisc(DVD)CSCA0101 Computing Basics18 Storage 17GB50 GBWavelength780nm650nm405nmRead/Write Speed1200 CD-ROM, CD-R CD-RW DVD-ROM DVD+R/RW DVD-R/RW DVD-RAM BD-R BD-RECSCA0101 Computing Basics19 Storage DevicesTertiaryStorageOpticalDiscCSCA010 1 Computing Basics20 Storage DevicesOff-lineStorage Alsoknownasdisconnectedstorage.

5 Isacomputerdatastorageonamediumoradevice thatisnotunderthecontrolofaprocessinguni t. Computing Basics21 Storage DevicesOff-lineStorage Alsoknownasdisconnectedorremovablestorag e. Isacomputerdatastorageonamediumoradevice thatisnotunderthecontrolofaprocessinguni t. Computing Basics22 Storage DevicesOff-lineStorage Examples: FloppyDisk Zipdiskette USBF lashdrive MemorycardCSCA0101 Computing Basics23 Storage DevicesOff-lineStorageFloppyDisk Asoftmagneticdisk. Floppydisksareportable. Floppydisksareslowertoaccessthanharddisk sandhavelessstoragecapacity,buttheyaremu chlessexpensive. Twocommonsizes:5 and3 .CSCA0101 Computing Basics24 Storage DevicesOff-lineStorageFloppyDisk5 inch Floppy Disk3 inch Floppy DiskCSCA0101 Computing Basics25 Storage DevicesOff-lineStorageZipDiskette "floppydrive. Capabletoholdupto100 MBofdataor250 MBofdataonnewdrives.

6 Computing Basics26 Storage DevicesOff-lineStorageUSBF lashDrive Asmall,portableflashmemorycardthatplugsi ntoacomputer sUSBportandfunctionsasaportableharddrive . Flashdrivesareavailableinsizessuchas256M B,512MB,1GB,5GB, Computing Basics27 Storage DevicesOff-lineStorageMemoryCard Anelectronicflashmemorystoragediskcommon lyusedinconsumerelectronicdevicessuchasd igitalcameras,MP3players,mobilephones,an dothersmallportabledevices. Memorycardsareusuallyreadbyconnectingthe devicecontainingthecardtoyourcomputer, Computing Basics28 Storage DevicesOff-lineStorageMemoryCardSecure Digital card (SD)MiniSDCompact FlashMemory StickMultiMediacardXD-Picture cardMemory card readerCSCA0101 Computing Basics29 Storage DevicesStorageDeviceFeatures Volatility Accessibility Mutability AddressabilityCSCA0101 Computing Basics30 Storage DevicesVolatility Twotypesofvolatility: VolatileMemory Non-VolatileMemoryCSCA0101 Computing Basics31 Storage DevicesVolatilityVolatileMemory Requiresconstantpowertomaintainthestored information.

7 Thefastestmemorytechnologies. Allcontentsareerasedwhenthesystem'spower isturnedofforinterrupted. Computing Basics32 Storage DevicesVolatilityNon-VolatileMemory Willretainthestoredinformationevenifitis notconstantlysuppliedwithelectricpower. Nonvolatilememoryisthedevicewhichkeepsth edataevenwhenthecurrentisoff. Computing Basics33 Storage DevicesAccessibility Referstoreadingorwritingdatarecords Twotypesofaccessibility: Randomaccess SequentialaccessCSCA0101 Computing Basics34 Storage DevicesAccessibilityRandomAccess Anylocationinstoragecanbeaccessedatanymo mentinapproximatelythesameamountoftime. Computing Basics35 Storage DevicesAccessibilitySequentialAccess Theaccessingofpiecesofinformationwillbei naserialorder,oneaftertheother;therefore thetimetoaccessaparticularpieceofinforma tiondependsuponwhichpieceofinformationwa slastaccessed.

8 Computing Basics36 Storage DevicesMutability Allowsinformationtobeoverwrittenatanytim e. Acomputerwithoutsomeamountofread/writest orageforprimarystoragepurposeswouldbeuse lessformanytasks. Threetypesofmutability: Read/writestorageormutablestorage Readonlystorage Slowwrite,fastreadstorageCSCA0101 Computing Basics37 Storage DevicesMutabilityRead/WriteStorageorMuta bleStorage Allowsinformationtobeoverwrittenatanytim e. Computing Basics38 Storage DevicesMutabilityReadOnlyStorage Retainstheinformationstoredatthetimeofma nufacture,andwriteoncestorage(WORM)allow stheinformationtobewrittenonlyonceatsome pointaftermanufacture. Computing Basics39 Storage DevicesMutabilitySlowWrite,FastReadStora ge Read/writestoragewhichallowsinformationt obeoverwrittenmultipletimes, Computing Basics40 Storage DevicesAddressability Threetypesofaddressability Location-addressable Fileaddressable Content-addressableCSCA0101 Computing Basics41 Storage DevicesAddressabilityLocation-addressabl e Computing Basics42 Storage DevicesAddressabilityFileaddressable Informationisdividedintofilesofvariablel ength, Computing Basics43 Storage DevicesAddressabilityContent-addressable Eachindividuallyaccessibleunitofinformat ionisselectedbasedonthebasisof(partof)th econtentsstoredthere.

9 Content-addressablestoragecanbeimplement edusingsoftware(computerprogram)orhardwa re(computerdevice),withhardwarebeingfast erbutmoreexpensiveoption. Hardwarecontentaddressablememoryisoftenu sedinacomputer' Computing Basics44 Storage DevicesOtherExampleofStorageDevices Punchcard Cloudstorage RAIDCSCA0101 Computing Basics45 Storage DevicesOtherExampleofStorageDevicesPunch edCard Earlymethodofdatastorageusedwithearlycom puters PunchcardsalsoknownasHollerithcards Containingseveralpunchedholesthatreprese ntsdataCSCA0101 Computing Basics46 Storage DevicesOtherExampleofStorageDevicesCloud Storage Cloudstoragemeans"thestorageofdataonline inthecloud,"whereinadataisstoredinandacc essiblefrommultipledistributedandconnect edresourcesthatcompriseacloud. Cloudstoragecanprovidethebenefitsofgreat eraccessibilityandreliability;rapiddeplo yment;strongprotectionfordatabackup, Computing Basics47 Storage DevicesOtherExampleofStorageDevicesCloud Storage Examples: GoogleDrive Flickr MicrosoftSkyDriveCSCA0101 Computing Basics48 Storage DevicesOtherExampleofStorageDevicesRAID RAID isshortforredundantarrayofindependent(or inexpensive)disks.

10 Itisacategoryofdiskdrivesthatemploytwoor moredrivesincombinationforfaulttolerance andperformance. RAID diskdrivesareusedfrequentlyonserversbuta ren'tgenerallynecessaryforpersonalcomput ers. RAID allowsyoutostorethesamedataredundantly(i nmultiplepaces)inabalancedwaytoimproveov erallstorageperformance.