A cloud service/delivery model represents a specific, pre-packaged combination of IT resources offered by a cloud provider. The cloud computing technology provides particular types of services that users can access on cloud platform.
The service models in cloud computing are categorized into three different types:
- Software as a Service (SaaS)
- Platform as a Service (Paas)
- Infrastructure as a Service (IaaS)
1. Software as a Service (SaaS) :
A software program positioned as a shared cloud service and made available as a “product” or generic utility represents the typical proﬁle of a SaaS offering. It is also known as “on-demand software” or “pay-as-you-go application”.
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. Cloud applications allow the cloud to be leveraged for software architecture, reducing the burdens of maintenance, support, and operations by having the application run on computers belonging to the vendor.
Advantages of SaaS Cloud Computing :
- Hardware requirement is less
- Easy to purchase
- Low maintenance cost
- No special software or version required
Disadvantages of Cloud Computing :
- Less Secure as compared to in house developement
- Switching between SaaS vendors is difficult
- No internet connection, No SaaS
- Latency Issue due to distance
2. Platform as a Service (Paas) :
The PaaS delivery model represents a pre-defined “ready-to-use” environment typically comprised of already deployed and configured IT resources. Specifically, PaaS relies on the usage of a ready-made environment that establishes a set of pre-packaged products and tools used to support the entire delivery lifecycle of custom applications.
In PaaS cloud computing platform, back end scalability is handled by the cloud service provider and the end user does not have to worry about to manage the infrastructure.Some examples of PaaS are App-Engine of Google & Force.com, Windows Azure, AppFog, Openshift and VMware Cloud Foundary.
Advantages Of PaaS Cloud Computing :
- Simply and easy to use
- Scalability of users ranges from hundreds to thousands without any changes to the applications
- PaaS providers facilitates user providing online communities where developer can get new ideas & share their experience & advice.
- Less investment in hardware and software.PaaS only requires a computer & a good internet connection
- Pre-built business functionality for users to directly start the project.
Disadvantages Of PaaS Cloud Computing :
- Migration from one PaaS vendors’ application to another PaaS vendor will create some problem.
- Privacy risk of data is there, if it is not located within the walls of the company
- Complexity can be there as some of the applications developed are local while others are from cloud.
3. Infrastructure as a Service (IaaS) :
IaaS gives business access to vital web architecture, such as storage space, servers, and connections, without the business need of purchasing and managing this internet infrastructure themselves. In simple words, IaaS lets you rent IT infrastructure – servers and virtual machines, storage, networks and operating systems – from a cloud provider on a pay-as-you-go basis.Organizations make use of the unlimited storage potential of the cloud infrastructure. They can expand and shrink their storage space as needed without having to worry about dedicated servers on site.
Advantages of IaaS Cloud Computing :
- As per needs , user can dynamically choose a CPU, memory and storage configuration.
- Users can easily access the vast cloud computing power.
- Flexible and efficient while renting IT infrastructures.Need of investment in rarely used IT hardware can be eliminated
Disadvantages Of IaaS Cloud Computing :
- Dependency on internet connection
- Dependency on virtualisation services
- It limits the user privacy and customization options.