基于闪存数据库系统调研报告

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1、Somekey-valuestoresusinglog-structureZhichaoLiangfrankey0207@gmail.comLevelDBRiakOutlineWhylogstructure?Riak:log-structurehashtableRethinkdb:log-structureb-treeLeveldb:log-structuremergetreeConclusionOutlineWhylogstructure?Riak:log-structurehashtableRethinkdb:log-structureb-treeLeveld

2、b:log-structuremergetreeConclusionLogStructureAlog-structuredfilesystemisafilesystemdesignfirstproposedin1988byJohnK.OusterhoutandFredDouglis.Designforhighwritethroughput,allupdatestodataandmetadataarewrittensequentiallytoacontinuousstream,calledalog.Conventionalfilesystemstendtolayout

3、fileswithgreatcareforspatiallocalityandmakein-placechangestotheirdatastructures.LogStructureforSSDRandomwritedegradesthesystemperformanceandshrinksthelifetimeofssd.Logstructureisssd-friendlynatively!MagneticDiskSSDfreefreefreefreefreefreefreefreefreefreefreefreedata1newdata1data2data3d

4、ata4newdata3blockblockdata3data2data1RAMfreefreefreedata2erasederasederasednewdata1data2data3data3OutlineWhylogstructure?Riak:log-structurehashtableRethinkdb:log-structureb-treeLeveldb:log-structuremergetreeConclusionRiak?Riakisanopensource,highlyscalable,fault-tolerantdistributeddatab

5、ase.Supportedcorefeatures:-operateinhighlydistributedenvironments-nosinglepointoffailure-highlyfault-tolerant-scalessimplyandintelligently-highlydataavailable-lowcostofoperationsBitcaskABitcaskinstanceisadirectory,andonlyoneoperatingsystemprocesswillopenthatBitcaskforwritingatagiventim

6、e.Theactivefileisonlywrittenbyappending,whichmeansthatsequentialwritesdonotrequirediskseeking.HashIndex:keydirAkeydirissimplyahashtablethatmapseverykeyinaBitcasktoafixed-sizestructuregivingthefile,offsetandsizeofthemostrecentlywrittenentryforthatkey.MergeThemergeprocessiteratesoveralln

7、on-activefileandproducesasoutputasetofdatafilescontainingonlythe“live”orlatestversionsofeachpresentkey.OutlineWhylogstructure?Riak:log-structurehashtableRethinkdb:log-structureb-treeLeveldb:log-structuremergetreeConclusionRethinkDB?RethinkDBisapersistent,industrial-strengthkey-values