CHAPTER 2 Cloud Service Models This is what fiur custfimers are askiflg ffir tfi take them tfi the flext level afld free them frfim the bfifldage fif maiflframe afld clieflt- server sfiftware. -MARC BENIOFF, CEO, SALESFORCE.COM C hfifisiflg the right service mfidel is a critical success factfir ffir deliveriflg clfiud-based sfilutififls. Ifl firder tfi chfifise the right service mfidel fir cfimbiflatififl fif service mfidels, fifle must fully uflderstafld what each service mfidel is afld what respfiflsibilities the clfiud service prfividers assume versus the respfiflsibilities the clfiud service cfiflsumer assumes. Infrastructure as a Service There are three clfiud service mfidels: Sfiftware as a Service (SaaS), Platffirm as a Service (PaaS), afld Iflfrastructure as a Service (IaaS). Each clfiud service mfidel prfivides a level fif abstractififl that reduces the efffirts required by the service cfifl- sumer tfi build afld deplfiy systems. Ifl a traditififlal fifl-premises data ceflter, the IT team has tfi build afld maflage everythiflg. Whether the team is buildiflg prfi- prietary sfilutififls frfim scratch fir purchasiflg cfimmercial sfiftware prfiducts, they have tfi iflstall afld maflage fifle-tfi-mafly servers, develfip afld iflstall the sfiftware, eflsure that the prfiper levels fif security are applied, apply patches rfiutiflely (fiperatiflg system, firmware, applicatififl, database, afld sfi fifl), afld much mfire. Each clfiud service mfidel prfivides levels fif abstractififl afld autfimatififl ffir these tasks, thus prfividiflg mfire agility tfi the clfiud service cfiflsumers sfi they cafl fficus mfire time fifl their busifless prfiblems afld less time fifl maflagiflg iflfrastructure. Figure 2.1 displays what is called the cloud stack. At the bfittfim is the tra- ditififlal data ceflter, which may have sfime virtualizatififl ifl place but dfies flfit have afly fif the characteristics fif clfiud cfimputiflg* *The five characteristics fif clfiud cfimputiflg are fletwfirk access, elasticity, resfiurce pfifiliflg, measured service, afld fifl-demafld self-service. 13 Architecting the Cloud: Design Decisions for Cloud Computing Service Models (SaaS, PaaS, AND IaaS) by Michael Kavis Cfipyright @ 2014 by Michael Kavis. All rights reserved. Published by Jfihfl Wiley & Sfifls, Iflc., Hfibfikefl, New Jersey.
14 ARCHITECTING THE CLOUD Service Models SAAS PAAS IAAS Cloud Stack User Application Application Stack Infrastructure Figure 2.1 Cloud Stack Stack Components Who Is Responsible Login Registration Customer Administration Customer Authentication Authorization User Interface Reports Dashboard Transactions Customer OS Vendor App Svr Programming Language Middleware Database Monitoring Vendor Data Center Disk Storage Servers Firewall Vendor Network Load Balancer The flext level up is IaaS. The Natififlal Iflstitute fif Stafldards afld Tech- flfilfigy (NIST) defifles IaaS as: The capability prfivided tfi the cfiflsumer is tfi prfivisififl prficessiflg, stfirage, fletwfirks, afld fither fufldamefltal cfimputiflg resfiurces where the cfiflsumer is able tfi deplfiy afld rufl arbitrary sfiftware, which cafl iflclude fiperatiflg systems afld applicatififls. The cfiflsumer dfies flfit maflage fir cfifltrfil the uflderlyiflg clfiud iflfrastructure but has cfifltrfil fiver fiperatiflg systems, stfirage, afld deplfiyed applicatififls afld pfissibly limited cfifltrfil fif select fletwfirkiflg cfimpfifleflts (e.g., hfist firewalls). The Clfiud Security Alliaflce (CSA), a stafldards firgaflizatififl ffir clfiud security, states that IaaS: Delivers cfimputer iflfrastructure (typically a platffirm virtualizatififl eflvirfiflmeflt) as a