Cloud Computing Service Models
中文版：云计算服务模式
The cloud offers three different services: Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a Service (IaaS).
SaaS — Software as a Service
- Also known as cloud application services; represents the most commonly utilized option for businesses in the cloud market.
- Provides license to an application to a customer through subscription or on a pay-as-you-go basis on-demand.
- Utilizes the internet to deliver applications managed by a third-party vendor.
- Some providers are Microsoft, Oracle, and IBM.
Delivery
Due to its web delivery model, SaaS eliminates the need to have IT staff download and install applications on each individual computer. Vendors manage all potential technical issues, such as data, middleware, servers, and storage.
Advantages
- Greatly reduces the time and money spent on tedious tasks such as installing, managing, and upgrading software.
Characteristics
- Managed from a central location
- Hosted on a remote server
- Accessible over the internet
- Users not responsible for hardware or software updates
Limitations and Concerns
- Interoperability
- Vendor lock-in
- Lack of integration support
- Data security
- Customization
- Lack of control
- Feature limitations
- Performance and downtime
Examples
- Google GSuite (Apps)
- Dropbox
- Salesforce
- Cisco WebEx
- SAP Concur
- GoToMeeting
PaaS — Platform as a Service
- Provides a platform to the users to develop, run, and maintain their applications.
- Accessed through a web browser by the users.
- Users are charged on a pay-per-use basis.
- All servers, storage, and networking can be managed by the enterprise or a third-party provider while the developers maintain management of the applications.
- Some providers are Amazon, Google, AppFog, and Heroku.
Delivery
The delivery model is similar to SaaS, except instead of delivering software over the internet, PaaS provides a platform for software creation. Developers can concentrate on building software without worrying about operating systems, software updates, storage, or infrastructure.
Advantages
- Simple, cost-effective development and deployment of apps
- Scalable
- Highly available
- Developers can customize apps without the headache of maintaining the software
- Significant reduction in the amount of coding needed
- Automation of business policy
- Easy migration to the hybrid model
Characteristics
- Builds on virtualization technology, so resources can easily be scaled up or down
- Provides a variety of services to assist with development, testing, and deployment
- Accessible to numerous users via the same development application
- Integrates web services and databases
Limitations and Concerns
- Data security
- Integrations
- Vendor lock-in
- Customization of legacy systems
- Runtime issues
- Operational limitation
Examples
- AWS Elastic Beanstalk
- Windows Azure
- Heroku
- Force.com
- Google App Engine
- OpenShift
IaaS — Infrastructure as a Service
- Provides consumers with computing resources: servers, networking, data center space, and storage on a pay-per-use and self-service basis.
- Clients use them as an outsourced service on-demand rather than purchasing these resources.
- Resources are provided either as dedicated or shared (virtual) resources.
- Some providers are Amazon, Google, IBM, Oracle, Fujitsu, and Hewlett-Packard.
Delivery
Delivers cloud computing infrastructure through virtualization technology. Clients are given complete control over the entire infrastructure via a dashboard or an API.
Advantages
- The most flexible cloud computing model
- Easy to automate deployment of storage, networking, servers, and processing power
- Hardware purchases can be based on consumption
- Clients retain complete control of their infrastructure
- Resources can be purchased as-needed
- Highly scalable
Characteristics
- Resources are available as a service
- Cost varies depending on consumption
- Services are highly scalable
- Multiple users on a single piece of hardware
- Organization retains complete control of the infrastructure
- Dynamic and flexible
Limitations and Concerns
- Security
- Legacy systems operating in the cloud
- Internal resources and training
- Multi-tenant security
Examples
- DigitalOcean
- Linode
- Rackspace
- Amazon Web Services (AWS)
- Cisco Metacloud
- Microsoft Azure
- Google Compute Engine (GCE)
Related Concepts
- Cloud Deployment Models — Public, Private, Hybrid