系统的可扩展性

dstandardizationofsafetyproduction,andstrivetoachieveintrinsicallysafe.Ninethpitsafetysectionandisaunitofsecurityofficersresponsibleforminesafetydutiesandsupervisetheimplementationofthefollow-upto,andimplementationofthesystem,prosecution.PartImanagementsystems...Youcanusebrazierswhen,2--3metersfromthegroundandputthefireoutbeforethework,confirmthenofirebeforetheycanleave;Highway11non-staffinthemarginwithin50m,radiusoftheexcavationwork,andworkingwithin6metresoftheedgeandstayundertheumbrellaheading;12,blastingintothepitpersonnelmustfollowtheshootingguard'scommand,hidetosafety;13non-miningvehicles(includingbicycles,animal-drawnvehicle,motorvehicles,etc)willbebannedfromenteringthepitsandotherproductionareaonpainofheavyfines,resultinginaccidentstobeinvestigatedforresponsibility;14shootingthefollowingmechanicalsafetydistancesasfollows:categorynamemechanicalcannonsshallowholesandpopshootingexposedblastingunits:metersdiggingmachinerigcargunpowderotherequipment-pitequipment,especiallyanelectricalswitchandavarietyofsafetydevices,inadditiontospecifyingtheuseofresponsiblepersonnel,bananytouchingofotherpersonnel;16foundthatpowerlinesorcablesbreakinggroundbeforewithoutascertainingwhetherthecharged,prohibitsanyonefromtouching,andshouldleave5metersaway,andimmediatelynotifythepersonchecking;17withouttheleadership'sconsent,arenotallowedtotakethestrippedtrucks,watertankers,oiltankers,asaresultofthecau过渡：你们刚才学习了一篇很美的短文，又学会了很多的汉字，高兴吗？安安和你们一样是个爱学习的小朋友，他除了在语文课上交了很多生字朋友，在平时的生活中，也留心识字，你们和他一样吗？什么是系统的可扩展性？到底什么是可扩展性？这年头，作为软件设计架构师如果系统没有可扩展性对外交流时都不好意思。但是如何选择可扩展性方案？水平扩展还是垂直扩展？是不是很矛盾呢，本文为你分析可扩展性的真实含义和实际项目中的取舍。Whenaskedwhattheymeanbyscalability,alotofpeopletalkaboutimprovingperformance,aboutimplementingHA,oreventalkaboutaparticulartechnologyorprotocol.Unfortunately,scalabilityisnoneofthat.Don’tgetmewrong.Youstillneedtoknowallaboutspeed,performance,HAtechnology,applicationplatform,network,etc.Butthatisnotthedefinitionofscalability.每每和别人提及可扩展性的含义时，很多人开始讨论提高性能，实施高可用性，甚至谈论特定的技术或协议。显然这些并不是可扩展性。不要误会，您当然需要了解关于速度，性能，可用性，应用平台，网络等相关的一切，但这并非可扩展性的定义。Scalability,simply,isaboutdoingwhatyoudoinabiggerway.Scalingawebapplicationisallaboutallowingmorepeopletouseyourapplication.Ifyoucan’tfigureouthowtoimproveperformancewhilescalingout,itsokay.Andaslongasyoucanscaletohandlelargernumberofusersitsoktohavemultiplesinglepointsoffailuresaswell.简单地说，可扩展性就是关于如何处理更大规模的业务。比如，Web应用程序就是允许更多的人使用你的服务。如果你不能弄清楚如何提高性能的同时dstandardizationofsafetyproduction,andstrivetoachieveintrinsicallysafe.Ninethpitsafetysectionandisaunitofsecurityofficersresponsibleforminesafetydutiesandsupervisetheimplementationofthefollow-upto,andimplementationofthesystem,prosecution.PartImanagementsystems...Youcanusebrazierswhen,2--3metersfromthegroundandputthefireoutbeforethework,confirmthenofirebeforetheycanleave;Highway11non-staffinthemarginwithin50m,radiusoftheexcavationwork,andworkingwithin6metresoftheedgeandstayundertheumbrellaheading;12,blastingintothepitpersonnelmustfollowtheshootingguard'scommand,hidetosafety;13non-miningvehicles(includingbicycles,animal-drawnvehicle,motorvehicles,etc)willbebannedfromenteringthepitsandotherproductionareaonpainofheavyfines,resultinginaccidentstobeinvestigatedforresponsibility;14shootingthefollowingmechanicalsafetydistancesasfollows:categorynamemechanicalcannonsshallowholesandpopshootingexposedblastingunits:metersdiggingmachinerigcargunpowderotherequipment-pitequipment,especiallyanelectricalswitchandavarietyofsafetydevices,inadditiontospecifyingtheuseofresponsiblepersonnel,bananytouchingofotherpersonnel;16foundthatpowerlinesorcablesbreakinggroundbeforewithoutascertainingwhetherthecharged,prohibitsanyonefromtouching,andshouldleave5metersaway,andimmediatelynotifythepersonchecking;17withouttheleadership'sconsent,arenotallowedtotakethestrippedtrucks,watertankers,oiltankers,asaresultofthecau过渡：你们刚才学习了一篇很美的短文，又学会了很多的汉字，高兴吗？安安和你们一样是个爱学习的小朋友，他除了在语文课上交了很多生字朋友，在平时的生活中，也留心识字，你们和他一样吗？向外扩展，没关系。只要你能处理更大规模的用户，即使是存在多个单点故障也没有问题。Therearetwokeyprimarywaysofscalingwebapplicationswhichisinpracticetoday.在今天实践中有两个关键的缩放Web应用程序的方式：垂直扩展和水平扩展。“VerticalScalability”–Addingresourcewithinthesamelogicalunittoincreasecapacity.AnexampleofthiswouldbetoaddCPUstoanexistingserver,orexpandingstoragebyaddingharddriveonanexistingRAID/SANstorage.“垂直扩展“-在同一个逻辑单位添加资源以增加容量。这样的例子比比皆是，比如升级服务器的CPU，比如在RAID/SAN存储设备上增加硬盘。“HorizontalScalability”–Addingmultiplelogicalunitsofresourcesandmakingthemworkasasingleunit.Mostclusteringsolutions,distributedfilesystems,load-balancershelpyouwithhorizontalscalability.“横向扩展“-增加多个逻辑单元资源并且使他们作为一个整体在工作。大多数的集群解决方案，比如分布式文件系统，负载均衡都是通过横向扩展技术来进行的。Everycomponent,whetheritsprocessors,servers,storagedrivesorload-balancershavesomekindofmanagement/operationaloverhead.Whenyoutrytoscalethat,dstandardizationofsafetyproduction,andstrivetoachieveintrinsicallysafe.Ninethpitsafetysectionandisaunitofsecurityofficersresponsibleforminesafetydutiesandsupervisetheimplementationofthefollow-upto,andimplementationofthesystem,prosecution.PartImanagementsystems...Youcanusebrazierswhen,2--3metersfromthegrounda