数据库系统原理(英文)-11-09.pptVIP免费

PART4DATASTORAGEANDQUERYApril2009DatabaseSystemConcepts-Chapter11StorageandFileStructures2IntroductiontoChapter11andChapter12InviewofphysicalDB,twoissuesshouldbeaddresseddataorganizationinDBS,i.e.physicalstoragestructureofdata—Chapter11dataaccessinDBS—Chapter12Chapter11StorageandFileStructureApril2009DatabaseSystemConcepts-Chapter11StorageandFileStructures4MainContentsinThisChapter11-I.PhysicalstoragemediainDBS(§11.1—§11.4)storage-devicehierarchy,disk,RAID11-II.Storageaccess11-III.Fileorganizationatphysicallevel11-IV.Organizationofrecordsinfilesatlogicallevel,i.e.filestructures11-IV.Data-dictionary(§11.8)April2009DatabaseSystemConcepts-Chapter11StorageandFileStructures5§11.1PhysicalStorageMedia11-I-1.Storage-devicehierarchy(§11.1)AsshowninFig.11.1Hierarchyprimarystorage,secondarystorage,tertiarystoragePerformanceindexreliability,speed,capacity,costFig.11.1Storage-devicehierarchyCPUsecondarystorageslowfastSpeedCapacitylargesmalllowhighCostReliabilityvolatilenonvolatiletertiarystoragePerformanceIndex:StorageprimarystorageApril2009DatabaseSystemConcepts-Chapter11StorageandFileStructures7ThediskstructureisshowninFig.11.2AccesstimeistakenastheperformancemeasuresofdisksthetimeittakesfromwhenareadorwriterequestisissuedtowhendatatransferbeginsAccesstimeincludesseektime–timeittakestorepositionthearmoverthecorrecttrack.4to10millisecondsontypicaldisksrotationallatency–timeittakesforthesectortobeaccessedtoappearunderthehead.4to11millisecondsontypicaldisks(5400to15000r.p.m.)11-I-2MagneticDisk11-I-2MagneticDiskFig.11.2Moving-headdiskmechanism磁柱seekingrotation(1)(4)(3)(2)(5)April2009DatabaseSystemConcepts-Chapter11StorageandFileStructures9Data-transferrate–therateatwhichdatacanberetrievedfromorstoredtothedisk,e.g.ATA-5:66MB/second,SCSI-3:40MB/sfiberChannel:256MB/sMeantimetofailure(MTTF)–theaveragetimethediskisexpectedtoruncontinuouslywithoutanyfailure.typically3to5yearsDataistransferredbetweendiskandmainmemor...