Preface
We always hear about the 3 models of cloud computing services:
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IaaS: Infrastructure-as-a-Service
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PaaS: Platform-as-a-Service
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SaaS: Software-as-a-Service
We can also see various analogies: eating pizza, eating hamburgers, eating barbecue, hot pot, building houses, decoration, writing documents, raising pigs, generating electricity, driving, having children??, picking up girls???... There are many different opinions, so is there a way to separate the true from the false and thoroughly understand these terms?
Yes, trace the source
I. Cloud Computing
The National Institute of Standards and Technology (NIST) provided a definition of cloud computing in 2011:
Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction.
That is to say, cloud computing is a model. It enables configurable computing resources (such as networks, servers, storage, applications, and services) to be accessed on-demand through the network. Only minimal management work or simple interaction with service providers is needed to quickly control the provisioning and release of these resources.
This cloud model consists of 5 essential characteristics, 3 service models, and 4 deployment models:
This cloud model is composed of five essential characteristics, three service models, and four deployment models.
Among them, the three service models are the so-called *aaS
II. 5 Essential Characteristics
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On-demand self-service: Consumers can unilaterally automatically provision computing capabilities, such as server time and network storage, as needed without requiring human interaction with each service provider
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Broad network access: Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, tablets, laptops, and workstations)
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Resource pooling: The provider's computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand. There is a sense of location independence in that the customer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction (e.g., country, state, or datacenter). Examples of resources include storage, processing, memory, and network bandwidth
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Rapid elasticity: Capabilities can be elastically provisioned and released to scale rapidly outward and inward commensurate with demand. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be appropriated in any quantity at any time
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Measured service: Cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and reported, providing transparency for both the provider and consumer of the utilized service
III. 3 Service Models
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Infrastructure as a Service (IaaS): The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, and deployed applications; and possibly limited control of select networking components (e.g., host firewalls)
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Platform as a Service (PaaS): The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages, libraries, services, and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly configuration settings for the application-hosting environment
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Software as a Service (SaaS): The capability provided to the consumer is to use the provider's applications running on a cloud infrastructure. The applications are accessible from various client devices through either a thin client interface, such as a web browser (e.g., web-based email), or a program interface. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings
The differences are mainly reflected in the degree of control users have over resources:
| Degree of Control | IaaS | PaaS | SaaS |
|---|---|---|---|
| Control (Needs Maintenance) | Operating Systems Applications Processing Storage Networks Other Fundamental Computing Resources | Deployed Applications Configuration Settings for Application-Hosting Environment | Some User-Specific Application Configuration Settings |
| Hosted (No Need to Worry About) | Network Components | Networks Servers Operating Systems Storage | Some Application Functions Networks Servers Operating Systems Storage |
From infrastructure to platform to software, the level of abstraction of resource supply forms becomes higher and higher, and users need to pay attention to fewer and fewer underlying facilities, as shown below:
IV. 4 Deployment Models
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Private cloud: The cloud infrastructure is provisioned for exclusive use by a single organization comprising multiple consumers (e.g., business units). It may be owned, managed, and operated by the organization, a third party, or some combination of them, and it may exist on or off premises
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Community cloud: The cloud infrastructure is provisioned for exclusive use by a specific community of consumers from organizations that have shared concerns (e.g., mission, security requirements, policy, and compliance considerations). It may be owned, managed, and operated by one or more of the organizations in the community, a third party, or some combination of them, and it may exist on or off premises
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Public cloud: The cloud infrastructure is provisioned for open use by the general public. It may be owned, managed, and operated by a business, academic, or government organization, or some combination of them. It exists on the premises of the cloud provider
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Hybrid cloud: The cloud infrastructure is a composition of two or more distinct cloud infrastructures (private, community, or public) that remain unique entities, but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds)
P.S. Cloud bursting is a configuration built between private cloud and public cloud to cope with IT demand peaks. If an organization using a private cloud reaches 100% of its resource capacity, the overflow traffic will be directed to the public cloud without interrupting services
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