DOC PREVIEW
ODU CS 775 - Study Notes

This preview shows page 1 out of 3 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 3 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 3 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

564CHAPTER12DISTRIBUTEDFILESYSTEMS12.5TowhatextentdoesSunNFSdeviatefromone-copyfileupdatesernafitip~?onstructascenarioinwhichtwouser-levelprocessessharingafilewouldoperatecorrectlyinasingleUNIXhostbutwouldobserveinconsistencies whenrunningin differenthosts.~p#ge54212.6SunNFSaims tosupportheterogeneousdistributedsystemsbytheprovisionofanoperatingsystem—independentfileservice.WhatarethekeydecisionsthattheimplementerofanNFSserverforanoperatingsystemotherthanUNIX~,,’vouldhavetake?WhatconstraintsshouldanunderlyingfilingsystemobeytobesuitablefortheimplementationofNFSservers?page53612.7WhatdatamusttheNFSclientmoduleholdonbehalfofeachuser-levelprocess?~pa~es5i36—537/12.8OutlineclientmoduleimplementationsfortheUNIXopen()andre~9systemcatusingtheNFSRPCcallsofFigure12.9,(i) withoutand(ii)withaclient~ache.~~ages5~8,54213.112.9ExplainwhytheRPC interfacetoearlyimplementationsofNFSispote~tiallyinsecure.13.2Thesecurity loopholehasbeenclosedinNFS3bytheuseofencr~tion.:owis~e13.3encryptionkeykeptsecret?Is thesecurityofthekeyadequate?1~j~ges~~13412.10AfterthetimeoutofanRPCcalltoaccessafileonahard-mountedfil~‘stemtheNFS135clientmoduledoesnotreturncontroltotheuser-levelprocessthatoriginatedthecall.Why?pag’53913.612.11HowdoestheNFS automounterhelp toimprovetheperformance~lscalabilityofNFS?page541ThisE12.12Howmanylookupcallsareneededtoresolveafive-partpathnañie~forexampleprOce~/usr/users/jim/code/xyz.c)forafilethatisstored onanNFSserver?W~iaiisthereasontheirforperformingthetranslationstep-by-step?page540differe12.13Whatconditionmustbefulfilledbytheconfigurationofthemounttai{ièsattheclientcomputersforaccesstransparencytobeachievedinanNFS-basedfihiii~gsystem?~omepage54012.14HowdoesAFSgaincontrolwhenanopenorclosesystemcallreferri~igtoatileinthespsharedfilespace isissuedbyaclient?~‘‘page549suppo12.15ComparetheupdatesemanticsofUNIXwhenaccessinglocalfiles~ith~thoseofNFSSystenandAFS.Underwhatcircumstancesmightclientsbecomeawareofthedifferences?fpages542,554navigadataar12.16HowdoesAFSdealwiththeriskthatcallbackmessagesmaybelost?page552112.17WhichfeaturesoftheAFSdesign makeitmorescalablethanNFS?W~arethelimitsX.500onitsscalability,assumingthatserverscan beaddedasrequited?Whicidevelopmentsoffergreaterscalability?pa~es54~5,556,561qg:i•~672CHAPTER15COORDINATIONANDAGREEMENT15.5Adaptthecentralserveralgorithmformutual exclusionto handletcrashfailureofL15.17Showticlient(inanystate),assumingthattheserveriscorrectandgiy~nareliablefailFIFO-ordetector.Commentonwhethertheresultantsystemisfault-to1~rant.What w.thecasehappenifaclientthatpossessesthetokeniswronglysuspectedtó~havêfailed?“.causally63615.8Suggest15.6Giveanexampleexecutionofthering-basedalgorithmtoshowthatprocessesaregroups.necessarily grantedentrytothecriticalsectioninhappened-before>6rder.pag~‘~15.19Indiscu15.7Inacertainsystem,eachprocesstypicallyusesacriticalsec~iok;inanytimesbefsubsetsj4;~..1~anotherprocessrequiresit.ExplainwhyRicartandAgrawalasmulticast-basedmumujilcasexclusionalgorithmisinefficientforthiscase,anddescribe ,l~ó*tojmproveperformance.Doesyouradaptationsatisfylivenesscondition~page6315.0Construc15.8Inthebullyalgorithm,arecoveringprocessstarts anelectionanE1~villbecometheiarehablccoordinatorifithasahigheridentifierthan thecurrentincumbeiit~Is thisanec...15.2Wegavefeatureofthealgorithm?pageswhichin15.9Suggesthowtoadapt thebullyalgorithmtodealwithtemporâ~’networkp~itiWhy,in.reliableh(slow communication)andslowprocesses...pageifwecou15.10DeviseaprotocolforbasicmulticastoverIPmulticast.page’consider15.11How,ifatall,shouldthedefinitionsofintegrity,agreementai~d~alidityorrelia15.22Considermulticastchangeforthecaseofopengroups?.~;page’whichus’proposed15.12Explainwhyreversingtheorderofthelines‘R-delivermai1~~f#≠~)then~valueNcmulticast(g,m);end~finFigure15.9makesthealgorithmno1oñg~rsatis~junifresult~eagreement. DoesthereliablemulticastalgorithmbasedonIPmu1~ic~ssatis1~’unifsysten’s~agreement?~.pagethusto th15.13ExplainwhetherthealgorithmforreliablemulticastoverIPmultistworksforopen15.23Showthawellasclosed groups.Givenanyalgorithmforclosedgroups, how,simply,canfaulty,ifderiveanalgorithmforopengroups?page’15.14ExplainhowtoadaptthealgorithmforreliablemulticastoverIP.multicasttoelimithehold-backqueue—sothatareceivedmessagethatisnotadupii~àtecanbedelivimmediately,butwithoutanyorderingguarantees.Hint:usesetsdf~equencenumtorepresentthemessagesthathavebeendeliveredsofar.,‘.:page15.15Considerhowtoaddresstheimpracticalassumptionswemadeiinordertomeetvalidityandagreementpropertiesforthereliable multicastprdt~ôco1basedonI?multicast.Hint:addarulefordeletingretainedmessageswhenthey~havebeedeliveverywhere,andconsideraddingadummy‘heartbeat’rncss~ge: whichisndeliveredtotheapplication,butwhichtheprotocolsendsiftheàjiplicationhasmessagetosend.~•.pag15.16ShowthattheFIFO-ordered multicast algorithmdoesnotworkforoyevlappingi~’byconsideringtwomessagessentfromthesamesourcetotwocw~1appinggroupsconsideringaprocessintheintersectionofthosegroups.Adapttheprotocoltoworkthiscase.Hint:processesshouldincludewiththeirmessagesthelatestsequnumbersofmessagessenttoallgroups.~.-page’EXERCISES673ishfái1u’i~e~fany15.17Showthat,ifthebasicmulticastthat weuseinthealgorithmofFigure15.13isalsotreliablefailure FIFO-ordered,thentheresultanttotally-ordered multicastisalsocausallyordered.Isitnt.What.~vouldthecasethatanymulticastthatisbothFIFO-orderedandtotallyorderedistherebyfailed?••Qagecausallyordered?page65515.18Suggesthowtoadapt thecausallyorderedmulticastprotocoltohandleoverlappingrocessesarenotgroups.page 657er.page’63715.19IndiscussingMaekawa’smutual exclusionalgorithm,wegaveanexampleofthreenytimesbeforesubsetsofasetofthreeprocessesthatcouldleadtoadeadlock.Usethesesubsetsasist-based~niutuamulticastgroupsto showhowapairwise total orderingisnotnecessarilyacyclic.toimproye’itspage658page63915.20Constructasolutiontoreliable,totallyorderedmulticastinasynchronoussystem,usingareliable multicastandasolutiontotheconsensusproblem. page659becomethenewthisane~essai~y15.21Wegaveasolutiontoconsensusfromasolutiontoreliableandtotallyorderedmulticast,page644which involvedselectingthefirstvaluetobedelivered.Explainfromfirstprincipleswhy,inanasynchronoussystemwecouldnotinsteadderiveasolutionbyusingatworkpartitionsreliablebut


View Full Document

ODU CS 775 - Study Notes

Download Study Notes
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Study Notes and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Study Notes 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?