Pracovní režim
InastandardC/Smodecomputernetwork,thenetworkservercanworkintwodifferentmodes:iterativemodeandconcur-rentmode).Thecircularmethodisthatonlyoneserverprocesscanrunintheserveratatime.Whenmultipleclientsrequestservice,theserverprocessrespondsintheorderoftherequest;theconcurrentmethodcanrunmultipleserverprocessesintheserveratthesametime,andEachserverprocessrespondstoaspecificclientrequest.
Thesetwoservermodelshavetheirownadvantagesanddisadvantages.Whentheservicetakesalongtime,ifacyclicserverisused,theclientwillnotreceiveafastresponse,andtheclientrequestmayevenberejected.However,thiskindofserverconsumesfewsystemresourcesandisrelativelysimpletoimplement.Theconcurrentservercreatesachildprocessforeachrequest,whichcanensurethatmultipleclientrequestsareprocessedatthesametime.Theuseofthisservermodelgenerallydoesnotcausetherejectionofclientrequests,butiffrequentchildprocessesarecreated,theburdenontheserverwillbeincreased..Inactualnetworkapplications,theserverneedstoprocessmultipleclientrequestsatthesametime,soitusuallyadoptsaconcurrentmethod.
Implementační technologie
Usually,thewebservercanadoptthefollowingfourimplementationtechnologies:
1)""Strategie okamžitého vytvoření, okamžitého zničení"", to znamená, že se server propojí s každým žádajícím klientem a vytvoří podproces pro každý požadavek klienta ke zpracování.
Aftertheconcurrentserverisstarted,thesystemdaemonmonitorswhetheraclientinitiatesaconnectionrequestonafixedport.Ifaclient'srequestisreceived,theserverdaemoncreatesachildprocesstohandletheclient'srequest,andthedaemoncontinuestomonitorconnectionrequestsfromotherclientsontheoriginalport.Afterthechildprocessfinishesservingtheclient,itclosestheconnection,releasestheresourcesitoccupied,andautomaticallyexits.
Obviously,thiskindofconcurrentserverhasthefollowingshortcomings:(1).Thesystemtimeisextended.Beforeprovidingservicestotheclientprocess,theserverparentprocessneedstocreateanewchildprocess,sotheclientprocessmustwaitatleastforthedelayofcreatingachildprocess.Forsomenetworkapplicationswithhighreal-timerequirements,suchatimedelaycannotbetolerated;(2)Thesourceoffailureislarge.Foreachclientprocessrequest,theserverparentprocessmustcreateanewchildprocess.Eachchildprocesstakesupalmostthesameresourcesastheparentprocess.Therefore,inmanysystems,thenumberofcreationprocessesislimited;(3)Theutilizationrateofthesourceislow.Thelackofaneffectiveinter-processcommunicationmechanismbetweentheparentprocessandthechildprocessmakestheparentprocessunabletoeffectivelycontrolthechildprocess.Atthesametime,thechildprocessterminatesitselfaftercompletingtheservicetotheclientprocessandcannotbereused.
2)Server předem vytváří procesy pro více dětí a zpracovává požadavky klientů. Tato metoda se nazývá „předvytvoření“.
Theserverbasedonthe"pre-creation"technologysolvestheproblemTheclientprocesswaitsforthedelayproblem,buttherearealsothefollowingproblems:(1)Theserveralwaysmaintainsafixednumberofchildprocesses,soevenifthereisnoconnectionrequestfromtheclientprocess,thesystemwillmaintaintheseidleprocesses,causingdamagetothesystem.Wasteofresources;(2)Thecivilserveronlyprovidesafixednumberofchildprocesses.Ifthenumberofclientconnectionrequestsexceedsthenumberofchildprocesses,thentheclientprocessmustwaitfortheserviceterminationofotherclientprocesses,whichmaycausegreaterdelay;(3Ifachildprocessexitsabnormally,thenumberofclientprocessconnectionsthattheservercansupportatthesametimewillbereducedby1,whichwillweakentheserver’sconcurrentprocessingcapabilities.
Inordertoovercometheaboveproblems,youcanusedynamic"pre-Creation"technology,thatis,theserverparentprocesscreatesacertainnumberofchildprocessesbasedontheresourcestatusofthesystemorthenumberofuserrequests,andthenputsthemina"pool"toforma"processpool".Whenaclientrequestarrives,Insteadofcreatinganewprocesstoserveit,itselectsanidleprocessfromthe"pool"toserveit.Aftertheserviceiscompleted,theprocessenterstheidlestate.Ifthenumberofclientssimultaneouslyrequestingisgreaterthanthenumberofprocessesintheprocesspool,thesystemAccordingtothestateofsystemresources,thenumberofprocessesinthe"pool"canbeincreased,orclientrequestscanbequeuedorsimplydiscarded,dependingonthespecificsituation.Theuseofthistechnologyspeedsuptheserver'sresponsetimeandimprovesresourcesTheutilizationefficiencyofthiseffectivelypreventstheserverfromcrashingduetoexcessiveclientrequests.
3)TheserverusesthefunctionselecttoimplementI/Omultiplexingformultipleclientconnections;
Inadditiontomulti-processormulti-threadedimplementationofconcurrentservers,I/Omultiplexingtechnologycanalsobeused.Throughthistechnology,thesystemkernelbuffersI/Odata.WhencertainI/OWhenready,thesystemwillnotifytheapplicationthattheI/Oisreadableorwritable,sothattheapplicationcancompletethecorrespondingI/Oimmediately,insteadofwaitingforthesystemtocompletethecorrespondingI/Ooperation,sothattheapplicationdoesnothavetowaitI/Ooperationisblocked.
Comparedwithmulti-processormulti-thread,thebiggestadvantageofI/Omultiplexingtechnologyisthatthesystemoverheadissmall.Thesystemdoesnotneedtocreateprocessesandthreads,anddoesnotneedtomaintaintheseProcessesandthreads,therebygreatlyreducingtheoverheadofthesystem.
4)Thesuperserveractivatesthestrategyoftheauxiliaryserver.
Thismodeofserverrequiresmultipleservers,oneofwhich(Thesuperserverwaitsfortherequestfromtheclientonawell-knownport.Oncethesuperserverreceivestheclient'srequest,itimmediatelyactivatesaslaveserverandtransferstheuser'srequesttotheactivatedslaveserver.ThentheslaveserverandtheclientprogramKeeptheconnectionandcompletetheprocessingoftheclient'srequest,andthesuperservercontinuestomonitortheclient'srequestontheoriginalport.
Inthisservermodel,eachslaveserverisstillaconcurrentserver,sotheconcurrencyofthesystemissignificantlyimproved.However,theuseofthisservermodelrequiresanincreaseinthenumberofservers,whichincreasesthecostofthesystemandisusuallyusedforsomeaccessArelativelylargenumberofwebservers.
Složení a rozdělení
Serverový software
Thedefinitionofserversoftwareisasmentionedabove,andtheserversoftwareworksinaclient-serverorbrowser-serverway,Therearemanyformsofservers,commonlyusedinclude:
Souborový server-jako Novell'sNetWare
Databázový server-jako je Oracledatabázový server, MySQL, PostgreSQL, MicrosoftSQLServer atd.
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Mailserver-Sendmail,Postfix,Qmail,MicrosoftExchange,LotusDomino atd.
Webový server-jako Apache,thttpd,MicrosoftIIS atd.
FTPserver-Pureftpd, Proftpd, WU-ftpd, Serv-U, VSFTP atd.
Aplikační server-jako Bea'sWebLogic,JBoss,Sun'sGlassFish
Proxyserver-jakoSquidcache
Computernameconversionserver-suchasMicrosoft'sWINSserver
Serverový hardware
Mostserversusecomponentredundancytechnology,RAIDtechnology,memoryerrorcorrectiontechnologyandmanagementsoftware.High-endserversusemulti-processorsandsupportasymmetricalprocessorstructurewithmorethandualCPUs.Whenselectingserverhardware,inadditiontoconsideringthegradeandspecificfunctionpositioning,youalsoneedtofocusonunderstandingthemainparametersandcharacteristicsoftheserver,includingprocessorarchitecture,scalability,serverstructure,I/0capabilities,andfailurerecoverycapabilities.Servertypescanbedividedaccordingtomultiplestandards.
1.Rozdělenopodleúrovněaplikaceneboměřítka
●Server základní úrovně: Server nejnižší úrovně, používaný hlavně pro kancelářské služby souborů a tisku.
●Server na úrovni pracovní skupiny: vhodný pro sítě malého rozsahu, vhodný pro poskytování webu, pošty a dalších služeb pro malé a středně velké podniky.
●Servery na úrovni oddělení: servery střední třídy, vhodná středně velká podniková datacentra, webové stránky a další aplikace.
●Server podnikové třídy: Špičkový server s možnostmi superzpracování dat, vhodný pro databázový server velké sítě.
2.Rozděleno podle struktury serveru
●Desktopserver:alsoknownastowerserver,thisisthemosttraditionalstructurewithbetterexpansionsex.
●Server namontovaný v racku: Server namontovaný v racku je instalován ve standardní 19palcové skříni. Podle výšky jsou specifikace 1U (1U=1,75 palce), 2U, 4U a 6U.
●Bladeserver:Vysoká dostupnost,vysoká hustota a nízkonákladová serverová platforma navržená pro speciální aplikační odvětví a prostředí počítačů s vysokou hustotou.Každý "blade" je ve skutečnosti základní deska systému.
●Skříňový server: Podvozek má skříňový typ, na server je třeba nainstalovat mnoho modulových komponent.
3.Dividedaccordingtohardwaretype
●Dedicatedserver:aspeciallydesignedhigh-levelserverwithaspecialoperatingsystem(suchasUNIX,MVS,VMS,etc.)),whichismainlyusedfordatabaseservicesandInternetbusiness.Generally,professionalcompaniesprovideafullsetofsoftwareandhardwaresystemsandfullservice.
●PCserver:AserverwithIntelorMotoroladedicatedprocessorsasthecore,compatiblewithavarietyofnetworkoperatingsystemsandnetworkapplicationsoftware,anditsperformancecanreachthelevelofmid-rangeRISCservers.
Význam slova diskriminace
Sometimes,wewillseeanotherconceptofwebserverwhichisdifferentfromwebserver.Thesetwodefinitionscancauseconfusion.Theformerreferstothecomputerusedforthewebsite,andthelatterreferstotheprogramthatincludessoftwaresuchasApache,whichrunsonacomputertomanagewebpagecomponentsandrespondtowebbrowserrequests.
Bezpečnostní opatření
(1)Makeabackupoftheserversystemfortimelyrestoration.
(2)Closeunnecessaryserviceportsandonlyopentherequiredports.
(3)Securitycheckforabnormalprocess,installandupdateserveroperatingsystemintime.
(4) Nainstalujte do systému software firewall a antivirový software.
(5)Openthelogservicetocheckthewhereaboutsofhackers.
(6)Implementationofencryptionandauthenticationsecuritytechnology.
Nepřímý vliv
Themajorsearchenginesarechoosingsomewebsiteswithbetteruserexperiencetomakebetterrankings.ThePVvalueofthewebsitedirectlyaffectstherankingofthewebsite.So,ifyouchooseaproductfromsuchahigh-qualityserverrenter,everyvisitorwillvisityourwebsiteataveryfastspeed,andthenaturalPVvaluewillbehigh.Thentheexperienceonyourwebsitewillnaturallybebetter.Ifeveryvisitorislikethis,thefriendlinessofthesearchenginewillgraduallyimprove.Thennaturallygivebetterweight.Therefore,high-qualitynetworkhostingspaceisthebasisforimprovingcustomerexperience.