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1、FLASH:AMainMemoryStorageSystemPyung-ChulKim,ByungGwanJung,MoonjaKimComputerTechnologyDivision,ETRI,P.O.Box106,Yusong,Taejon,305-600,KoreaE-mail:pckim@dbserver.etri.re.krAbstractInthispaper,weintroduceanewmainmemorystoragesystemcalledFLASHthatisdesignedforreal-timeapplications.
2、TheFLASHsystemischaracterizedbythememoryresidencyofdataandanewfastanddynamichashingschemecalledextendiblechainedbuckethashing.Wecomparedtheperformanceofthenewhashingalgorithmwithotherwell-knownones.Also,wecarriedoutanexperimenttocomparetheoverallperformanceoftheFLASHsystemwith
3、acommercialone.BothcomparisonresultsshowthatthenewhashingschemeandtheFLASHsystemoutperformsothercompetitives.-1-1.IntroductionGrowingattentionhasbeenpaidtomainmemorydatabasesystemsduetoitsfastresponsetimethatisnecessaryforreal-timeapplications,andtherapidlydecreasingcostofRAMs
4、.Althoughconventionaldatabasesystemshavebeenwidelyusedduetoitsscalabilitytosupportverylargedatabasesanduserfriendlyinterface,theirdependencyonsecondarystoragetostoreandaccessdatalimitsitsusageintosystemsinwhichthespeedofdiskI/Oisacceptable.Thetransactionresponsetimeinconventio
5、naldatabasesystemsislimitedbylatencydelayindisks,whichisusuallytheorderof10~20ms.Thismightbeenoughfortraditionalapplicationsinwhicharesponsetimeofafewsecondistolerable,butisunacceptableinreal-timeapplicationsthatrequireresponsewithinhundredsofmicroseconds.Thechallengetoovercom
6、ethehurdleoftheI/Oboundmakethesightofresearchersmovefromdisk-baseddatabasesystemstomemory-baseddatabasesystems[5].Inmemory-baseddatabasesystems,theentiredatabaseresidespermanentlyinmainmemory,therebyeliminatingdiskI/Os.Inordertosupportthememoryresidencyoftheentiredatabase,thes
7、izeofadatabasemustbesmallerthantheamountofavailablememory.Fortunately,assemiconductormemorybecomescheaperandthedensityincreases,itbecomesfeasibletostorerelativelylargedatabasesinmemory.Forlastseveralyears,networkinformationcontrol/managementsystem(NICS)hasbeendevelopedinourins
8、titutetoperformbothservicecontrolfunctionsandservicemanagemen