IaaS, PaaS and SaaS are cloud computing service models.
IaaS(Infrastructure as a service), as the name suggests, provides you the computing infrastructure, physical or (quite often) virtual machines and other resources like virtual-machine disk image library, block and file-based storage, firewalls, load balancers, IP addresses, virtual local area networks etc. Examples : Amazon EC2, Windows Azure, Rackspace.
PaaS(Platform as a service), as the name suggests, provides you computing platforms which typically includes operating system, programming language execution environment, database, web server etc. Examples : AWS Elastic Beanstalk, Heroku, Force.com, Google App Engine.
While in Saas(Software as a service) model you are provided with access to application softwares often referred to as on-demand softwares. You don’t have to worry about the installation, setup and running of the application. Service provider will do that for you. You just have to pay and use it through some client. Examples : Google Apps, Microsoft Office 365.
Few additional points regarding your question :
1- AWS(Amazon web services) is a complete suite which involves a whole bunch of useful web services. Most popular are EC2 and S3 and they belong to IaaS service model.
2- Although Hadoop is based on previous works by Google(GFS and MapReduce), it is not from Google. It is an Apache project. You can find more here. It is just a distributed computing platform and does not fall into any of these service models, IMHO.
3- Microsoft’s Windows Azure is again an example of IaaS.
As far as popularity of these services is concerned, they all are popular. It’s just that which one fits into your requirements better. For example, if you want to have a Hadoop cluster on which you would run MapReduce jobs, you will find EC2 a perfect fit, which is IaaS. On the other hand if you have some application, written in some language, and you want to deploy it over the cloud, you would choose something like Heroku, which is an example of PaaS.
IAAS (Infrastructure As A Service) :
•The base layer
•Deals with Virtual Machines, Storage (Hard Disks), Servers, Network, Load Balancers etc
PAAS (Platform As A Service) :
•A layer on top of IAAS
•Runtimes (like java runtimes), Databases (like mySql, Oracle), Web Servers (tomcat etc)
SAAS (Software As A Service) :
•A layer on top on PAAS
•Applications like email (Gmail, Yahoo mail etc), Social Networking sites (Facebook etc)
To quickly relate consider the below Google’s offerings:
IAAS : Google Compute Engine (One can develop programs to be run on high performing google’s computing infrastructure)
PAAS : Google App Engine (One can develop applications and let them execute on top of Google app engine which take care of the execution)
SAAS : Gmail, Google+ etc (One can use email services and extend email/google+ based applications to form newer applications)
Popularity
Company Wise Popularity
Cloud computing is dominated by
1.Amazon Web Services (AWS),
2.Google Compute Engine, Google App Engine
3.Microsoft Azure
4.There are many small and medium scale cloud operators that include IBM, Oracle etc.
Most of the popularity around these services owe to the reputation of the company and the amount of investments being made by these companies around the cloud space.
Type of Service Wise Popularity
1.PAAS (Platform as a Service) is more popular among developers as they can put all their concentration on developing their apps and leave the rest of management and execution to the service provider. Many service providers also offer the flexibility to increase/decrease the CPU power depending upon the traffic loads giving developers cost effective and easy & effortless management.
2.SAAS (Software as a service) is more popular among with consumers, who bother about using the application such as email, social networking etc
3.IAAS (Infrastructure as a service) is more popular among users into research and high computing areas.
I found a great explanation from the “Windows Azure Platform: Cloud Development Jump Start” series in the first video (the video series is available both on iTunes and Zune and it covers the latest 1.3.x version of the SDK). The series is provided free of charge. Below are a couple of slides from the presentation:
Easy to Understand one-word descriptions of each term (i.e. IaaS means host)
I really like the last slide, because it clearly breaks down hierarchy of software layers into what is each vendor service (IaaS, PaaS and SaaS) is responsible for and what you are responsible for. Also in the video one of the speakers (Manu Cohen-Yashar) breaks each service down by the “unit you are gaining” from the service:
IaaS – the unit you are gaining is a computer/server. Therefore IaaS is essentially a “physical server box”. An example of this would be going to RackSpace or SoftLayer and leasing a physical box from them. The vendor manages the networking, hard drives (if they fail), hardware of the box, virtualization O/S (if the box is virtualized). You can remote desktop to the box and you manage everything else (shown in the screenshot above). Windows Azure provides IaaS in the form the VM Role (you upload a Windows Server 2008 R2 image and manage the server yourself).
PaaS – the unit you are gaining is an application/framework. Therefore PaaS is a “hosted application/framework/tools that you can leverage to build something on. That application is configured on IIS/SQL Server etc and runs on a hardware/virtual system that the vendor manages. An example of PaaS would be Windows Azure (excluding the VM Role) services like web role, worker role, Reporting Services etc.
SaaS – the unit you are gaining is business functionality. For example, Gmail is a type of a SaaS mail provider because you don’t have to manage any service yourself and its all done by the vendor (Google in this example).
I really like the clear examples and distinct definitions that are made in the videos. Hopefully, you can use these examples in explaining this to your boss or a non-technical person. I highly recommend you check out the “Windows Azure Platform: Cloud Development Jump Start” series if you are interested on learning about Azure or gain general information on the cloud.
I am a strong believer of Cloud Computing. It is the trend of the IT industry, no matter hardware vendors or software vendors will eventually step in this filed or die. Actually, it is happening now. In the future, Cloud Computing will be just like the water, electricity and cable those daily things that we pay for monthly to get the services. And we can also easily move to another Cloud service provider that can provide better price and services. Currently, Saas, PaaS and Iaas are the three main categories of Cloud Computing Service Model in the market.
SaaS
Software as a Service (SaaS) is a software distribution model in which applications are hosted by a vendor or service provider and made available to customers over a network, typically the Internet.
SaaS is becoming an increasingly prevalent delivery model as underlying technologies that support Web services and service-oriented architecture (SOA) mature and new developmental approaches, such as Ajax, become popular. Meanwhile, broadband service has become increasingly available to support user access from more areas around the world.
SaaS is closely related to the ASP (application service provider) and on demand computing software delivery models. IDC identifies two slightly different delivery models for SaaS. The hosted application management (hosted AM) model is similar to ASP: a provider hosts commercially available software for customers and delivers it over the Web. In the software on demand model, the provider gives customers network-based access to a single copy of an application created specifically for SaaS distribution.
PaaS
Platform as a Service (PaaS) is a way to rent hardware, operating systems, storage and network capacity over the Internet. The service delivery model allows the customer to rent virtualized servers and associated services for running existing applications or developing and testing new ones.
Platform as a Service (PaaS) is an outgrowth of Software as a Service (SaaS), a software distribution model in which hosted software applications are made available to customers over the Internet. PaaS has several advantages for developers. With PaaS, operating system features can be changed and upgraded frequently. Geographically distributed development teams can work together on software development projects. Services can be obtained from diverse sources that cross international boundaries. Initial and ongoing costs can be reduced by the use of infrastructure services from a single vendor rather than maintaining multiple hardware facilities that often perform duplicate functions or suffer from incompatibility problems. Overall expenses can also be minimized by unification of programming development efforts.
On the downside, PaaS involves some risk of “lock-in” if offerings require proprietary service interfaces or development languages. Another potential pitfall is that the flexibility of offerings may not meet the needs of some users whose requirements rapidly evolve.
IaaS
Infrastructure as a Service (IaaS) is a provision model in which an organization outsources the equipment used to support operations, including storage, hardware, servers and networking components. The service provider owns the equipment and is responsible for housing, running and maintaining it. The client typically pays on a per-use basis. nfrastructure as a Service is sometimes referred to as Hardware as a Service (HaaS)
Some segments within the three major Cloud services.
IDaaS
Identity as a Service (IDaaS) is an authentication infrastructure that is built, hosted and managed by a third-party service provider. IDaaS can be thought of as single sign-on (SSO) for the cloud.
An IDaaS for the enterprise is typically purchased as a subscription-based managed service. A cloud service provider may also host applications for a fee and provide subscribers with role-based access to specific applications or even entire virtualized desktops through a secure portal.
SaaS
Storage as a Service (SaaS) is a business model in which a large company rents space in their storage infrastructure to a smaller company or individual.
In the enterprise, SaaS vendors are targeting secondary storage applications by promoting SaaS as a convenient way to manage backups. The key advantage to SaaS in the enterprise is in cost savings — in personnel, in hardware and in physical storage space. For instance, instead of maintaining a large tape library and arranging to vault (store) tapes offsite, a network administrator that used SaaS for backups could specify what data on the network should be backed up and how often it should be backed up. His company would sign a service level agreement (SLA) whereby the SaaS provider agreed to rent storage space on a cost-per-gigabyte-stored and cost-per-data-transfer basis and the company’s data would be automatically transferred at the specified time over the storage provider’s proprietary wide area network (WAN) or the Internet. If the company’s data ever became corrupt or got lost, the network administrator could contact the SaaS provider and request a copy of the data.
Storage as a Service is generally seen as a good alternative for a small or mid-sized business that lacks the capital budget and/or technical personnel to implement and maintain their own storage infrastructure. SaaS is also being promoted as a way for all businesses to mitigate risks in disaster recovery, provide long-term retention for records and enhance both business continuity and availability.
CaaS
Communications as a Service (CaaS) is an outsourced enterprise communications solution that can be leased from a single vendor. Such communications can include voice over IP (VoIP or Internet telephony), instant messaging (IM), collaboration and videoconference applications using fixed and mobile devices. CaaS has evolved along the same lines as Software as a Service (SaaS).
The CaaS vendor is responsible for all hardware and software management and offers guaranteed Quality of Service (QoS). CaaS allows businesses to selectively deploy communications devices and modes on a pay-as-you-go, as-needed basis. This approach eliminates the large capital investment and ongoing overhead for a system whose capacity may often exceed or fall short of current demand.
CaaS offers flexibility and expandability that small and medium-sized business might not otherwise afford, allowing for the addition of devices, modes or coverage on demand. The network capacity and feature set can be changed from day to day if necessary so that functionality keeps pace with demand and resources are not wasted. There is no risk of the system becoming obsolete and requiring periodic major upgrades or replacement.
SaaS
Security-as-a-service (SaaS) is an outsourcing model for security management. Typically, Security as a Service involves applications such as anti-virus software delivered over the Internet but the term can also refer to security management provided in-house by an external organization. Security as a Service product vendors include Cisco, McAfee, Panda Software, Symantec, Trend Micro and VeriSign
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