Using MEMS-based storage devices in computer syste

UsingMEMS-basedstoragedevicesincomputersystemsSTEVENW.SCHLOSSERMay2004cmu-pdl-04-104Dept.ofElectricalandComputerEngineeringCarnegieMellonUniversityPittsburgh,PA15213AdissertationsubmittedtothegraduateschoolinpartialfulllmentoftherequirementsforthedegreeofDoctorofPhilosophyinElectricalandComputerEngineering.ThesiscommitteeGregoryR.Ganger,ChairL.RichardCarleyJamesC.HoeCharlesC.Morehouse,Hewlett-PackardLaboratoriesc2004StevenW.SchlosseriKeywords:MEMS-basedstorage,storagesystemsperformance,databasesys-tems,diskarraysTomyfamily:myparents,PhilandKathy;mysister,Jennifer;andmywife,Rachel.AbstractMEMS-basedstorageisaninterestingnewtechnologythatpromisestobringfast,non-volatile,massdatastoragetocomputersystems.MEMS-basedstoragede-vices(MEMStores)themselvesconsistofseveralthousandread/writetips,anal-ogoustotheread/writeheadsofadiskdrive,whichreadandwritedatainarecordingmedium.ThismediumiscoatedonamovingrectangularsurfacethatispositionedbyasetofMEMSactuators.Accesstimesareexpectedtobelessthanamillisecondwithenergyconsumption10{100lessthanalow-powerdiskdrive,whilestreamingbandwidthandvolumetricdensityareexpectedtobearoundthatofdiskdrives.ThisdissertationexplorestheuseofMEMStoresincomputersystems,withafocusonwhethersystemscanuseexistingabstractionsandinterfacestoincor-porateMEMStoreseectively,oriftheywillhavetochangethewaytheyaccessstoragetobenetfromMEMStores.IfsystemscanuseMEMStoresinthesamewaythattheyusediskdrives,itwillbemorelikelythatMEMStoreswillbeadoptedwhentheydobecomeavailable.SincerealMEMStoresdonotyetexist,Ipresentadetailedsoftwaremodelthatallowstheirusetobeexploredunderavarietyofworkloads.Toanswerthequestionofwhetheranewtypeofdevicerequireschangestosystems,Ipresentamethodologythatincludestwoobjectivetestsfordeterminingwhetherthebenetfromadeviceisduetoaspecicdierenceinhowthatdeviceaccessesdataorisjustduetothefactthatthatdeviceisfaster,smaller,oruseslessenergythanivcurrentdevices.IpresentarangeofpotentialusesofMEMStoresincomputersystems,examiningeachunderanumberofuserworkloads,usingthetwoobjectiveteststoevaluatetheirecacy.Usingtheevidencepresentedandthetwoobjectivetests,IshowthatsystemscanincorporateMEMStoreseasilyandemploythesamestandardabstractionsandinterfacesusedwithdisksystems.Atahighlevel,theintuitionisthatMEMStoresaremechanicalstoragedevices,justlikediskdrives,onlyfaster,smaller,andre-quiringlessenergytooperate.Accessingdatarequiresaninitialseektimethatisdistance-dependent,and,onceaccesshasbegun,sequentialaccessisthemostecient.Thisintuitionisdescribedinmoredetail,andtheresultisshowntoholdfortherangeofusespresented.AcknowledgementsNotonewordofthisdissertationcouldhavebeenwrittenwithoutagreatdealofhelpandsupportfrommanypeople.BeingagraduatestudentintheParallelDataLaboratoryhasbeenthemostrewardingexperienceofmylife,andIamgratefulforhavinghadtheopportunitytoworkwithsuchafantasticgroup.Themostimportantthanksgotomycollaboratorandfriend,JohnLinwoodGrin.Westartedworkingonthisprojectin1999,builtthemodelandsimulatortogether,andproducedmanyoftheresultspresentedhere.Iwillalwaysbegratefulforhishelp,insight,andfriendship.IalsoowespecialthankstoJiriSchindler,MinglongShao,andNatassaAilamaki,whohavehelpedmeagreatdealinthelasttwoyearstoapplysometheinsightsofthisdissertationtodiskdrivesanddatabasesystems.Ihavebeenfortunatetohavethesupportofthemembersofmythesiscom-mittee,whohavebeencrucialtodevelopingthiswork.GregGanger,myadvisor,hastaughtmemorethanIeverthoughtIcouldknowaboutcomputersystems,storagedevices,andnavigatingtheworldofresearch.Inadditiontotakingontheresponsibilitiesofatleastfourfull-timejobssimultaneously,heisalwaysavailabletohisstudents,whichistrulyamazing.RickCarleyprovidedtheinitialimpetusforthisworkbystartingtheMEMS-basedstorageresearchprojectintheMEMSLaboratoryatCarnegieMellon.Hehadthegreatforesightofinvolvingcomputersystemsresearchersintheeort,whichledtothiswork.JamesHoewasinvalu-ableinllingtheroleoftheoutsider,makingsurethatIwascoveringalltherightvibases.I'vealsobeenfortunatetohavethesupportandinputofChuckMorehouse,wholeadstheprobestorageeortatHewlett-PackardLaboratories.IalsowanttothankDavidNagle,whonotonlyhelpedstartthisresearch,butalsomadeitpossibleformetoattendgraduateschool.ThestudentsandstaoftheParallelDataLaboratoryhavebeenveryhelpfulandsupportiveovertheyears.CraigSoules,BrandonSalmon,EnoThereska,MikeAbd-El-Malek,GarthGoodson,JayWylie,AndyKlosterman,ShuhengZhou,JohnStrunk,TedWong,DavidPetrou,andJohnBucy,haveallhelpedovertheyearsinwaystoonumeroustomention.LindaWhipkeyandKarenLindenfelserkeepouroceandlabrunningsmoothlyandIcan'tthankthemenoughfortheirhelp.ThanksalsotoJoanDigneywhoenduresourconstantlatenesswhenpreparingposters,butstillndsitinherhearttohelpastudentproofreadhisdissertation.Contents1Introduction11.1Thesisstatement............................31.2Overview................................31.2.1Rolesandpolicies.......................51.2.2Objectivetests.........................61.3Contributions..............................61.4Organization..............................72Background