L6-2

Lesson6NetworkStorageandCloudComputingText2TheDetailsofNetworkStorage要點(diǎn)KeyPoints：專業(yè)術(shù)語(yǔ)DAS、NAS位置無(wú)關(guān)的網(wǎng)盤(pán)Enhance、improve、drop、reduceRun、carryout、performCompute、computer、computation、computationalAclusteredfilesystemisafilesystemwhichissharedbybeingsimultaneouslymountedonmultipleservers.Thereareseveralapproachestoclustering,mostofwhichdonotemployaclusteredfilesystem(onlydirectattachedstorageforeachnode).Clusteredfilesystemscanprovidefeatureslikelocation-independentaddressing位置無(wú)關(guān)的尋址

andredundancywhichimprove

reliabilityorreducethecomplexityoftheotherpartsofthecluster.Parallelfilesystemsareatypeofclusteredfilesystemthatspreaddataacrossmultiplestoragenodes,usuallyforredundancyorperformance.mount（加載）指被操作系統(tǒng)識(shí)別，可被用戶訪問(wèn)。simultaneous同時(shí)的synchronous同步的asynchronous異步的“同步”指在通信中使用共同的時(shí)鐘approach在這里翻譯成“方法”,同way、method和means等，approach起源于ap去+proach接近。Afilehostingservice,cloudstorageservice,onlinefilestorageprovider,orcyberlockerisanInternethostingservicespecificallydesignedtohostuserfiles.Itallowsuserstouploadfilesthatcouldthenbeaccessedovertheinternetfromadifferentcomputer,tablet,smartphoneorothernetworkeddevice,bythesameuserorpossiblybyotherusers,afterapasswordorotherauthenticationisprovided.Typically,theservicesallowHTTPaccess,andsometimesFTPaccess.Relatedservicesarecontent-displayinghostingservices(i.e.videoandimage),virtualstorage,andremotebackup.Incomputing,afileserver(orfileserver)isacomputerattachedtoanetworkthathastheprimarypurposeofprovidingalocationforshareddiskaccess,i.e.sharedstorageofcomputerfiles(suchasdocuments,soundfiles,photographs,movies,images,databases,etc.)thatcanbeaccessedbytheworkstationsthatareattachedtothesamecomputernetwork.Thetermserverhighlightstheroleofthemachineintheclient–serverscheme,wheretheclientsaretheworkstationsusingthestorage.Afileserverisnotintendedtoperform

computationaltasks,anddoesnotrunprogramsonbehalfofitsclients.Itisdesignedprimarilytoenablethestorageandretrievalofdatawhilethecomputationiscarriedoutbytheworkstations.workstation是使用服務(wù)器（server）提供服務(wù)（service）的計(jì)算機(jī)，即客戶機(jī)（client）。workstation也指大（中、?。┬蜋C(jī)的終端，也指性能很好的個(gè)人計(jì)算機(jī)，例如圖形工作站（graphicworkstation）scheme組合、體制，client–serverscheme翻譯為“客戶機(jī)—服務(wù)器架構(gòu)”或“c/s架構(gòu)”。Fileserversarecommonlyfoundinschoolsandoffices,whereusersuseaLANtoconnecttheirclientcomputers.Network-AttachedStorage(NAS)isafile-levelcomputerdatastorageserverconnectedtoacomputernetworkprovidingdataaccesstoaheterogeneousgroupofclients.NASisspecializedforservingfileseitherbyitshardware,software,orconfiguration.Itisoftenmanufacturedasacomputerappliance–apurpose-builtspecializedcomputer.NASsystemsarenetworkedapplianceswhichcontainoneormorestoragedrives,oftenarrangedintological,redundantstoragecontainersorRAID.Thekeydifferencebetweendirect-attachedstorage(DAS)andNASisthatDASissimplyanextensiontoanexistingserverandisnotnecessarilynetworked.NASisdesignedasaneasyandself-containedsolutionforsharingfilesoverthenetwork.BothDASandNAScanpotentiallyincreaseavailabilityofdatabyusingRAIDorclustering.NASprovidesbothstorageandafilesystem.ThisisoftencontrastedwithSAN(StorageAreaNetwork),whichprovidesonlyblock-basedstorageandleavesfilesystemconcernsonthe“client”side.SANprotocolsincludeFibreChannel,iSCSI,ATAoverEthernet(AoE)andHyperSCSI.builtforaspecificpurpose可以簡(jiǎn)單地表達(dá)為purpose-builtfile-level文件級(jí)別，block-level（塊級(jí)別）或block-based，都是指數(shù)據(jù)的抽象程度（levelofabstraction），上層應(yīng)用（upperapplication）能使用（employ）的數(shù)據(jù)結(jié)構(gòu)（datastructure）SANisanetworkwhichprovidesaccesstoconsolidated,blockleveldatastorage.SANsareprimarilyusedtoenhancestoragedevices,suchasdiskarrays,tapelibraries,andopticaljukeboxes,accessibletoserverssothatthedevicesappeartotheoperatingsystemaslocallyattacheddevices.ASANtypicallyhasitsownnetworkofstoragedevicesthataregenerallynotaccessiblethroughthelocalareanetwork(LAN)byotherdevices.ThecostandcomplexityofSANsdroppedintheearly2000stolevelsallowingwideradoptionacrossbothenterprise