Cloud Computing
Cloud computing is basically delivery of computing services—servers, storage, databases, networking, software, analytics and more, over the Internet.
Companies offering these computing services are called cloud providers and typically charge for cloud computing services based on usage, similar to how you are billed for water or electricity at home.
Third-party clouds enable organizations to focus on their core businesses instead of expending resources on computer infrastructure and maintenance.
Cloud computing Service models
In cloud computing there are mainly three (3) models are there. are;
SAAS : Software As A Service
PAAS: Platform As A Service
IAAS : Infrastructure As A Service
SAAS : Software As A Service
The traditional model of software distribution, in which software is purchased for and installed on personal computers, is sometimes referred to as Software-as-a-Product.
SAAS is stand for Software As A Service. Software on demand refers to computer applications that are delivered as a service via the Internet. This type of software is also referred to as on-demand software, SaaS (Software-as-a-Service) and Applications-as-a-Service.
The efficiency gains delivered by software on demand frees up IT personnel for the more important task of managing IT resources as a strategic tool to optimize their business operations.
SaaS applications are sometimes called Web-based software, on-demand software, or hosted software. Whatever the name, SaaS applications run on a SaaS provider’s servers. The provider manages access to the application, including security, availability, and performance.
For accessing you simply access it via the Internet, freeing yourself from complex software and hardware management.
Characteristics
For better understanding on SAAS model simply think on bank model.It protects the privacy of each customers while providing service that is reliable and secure—on a massive scale.
A bank’s customers all use the same financial systems and technology without worrying about anyone accessing their personal information without authorization.
Architecture
SAAS have MULTITENANT ARCHITECTURE.
In SAAS architecture it provided Multitenant Architecture. In this architecture all users and applications share a single, common infrastructure and code base that is centrally maintained. The single application runs on a server and multiple user who have access can access and do there work on the application.
Easy Customization
SAAS user easily customize applications to fit their business processes without affecting the common infrastructure. Because of the way SaaS is architect-ed, these customization are unique to each company or user and are always preserved through upgrades. That means SaaS providers can make upgrades more often, with less customer risk and much lower adoption cost.
Example : SendGrid, Tivoli Live, SalesForce.com
PAAS : Platform As A Service
It is a cloud computing model in which a third-party provider delivers hardware and software tools. Usually it needed for application development — to users over the internet. A PaaS provider hosts the hardware and software on its own infrastructure. As a result, PaaS frees users from having to install in-house hardware and software to develop or run a new application.
Enterprise PaaS provides line-of-business software developers a self-service portal for managing computing infrastructure from centralized IT operations and the platforms that are installed on top of the hardware. The enterprise PaaS can be delivered through a hybrid model that uses both public IaaS and on-premise infrastructure or as a pure private PaaS that only uses the latter.
Architecture
On-demand self-service : End users can sign up and receive services without the long delays that have characterized traditional IT. It refers to the service provided by cloud computing vendors that enables the provision of cloud resources on demand whenever they are required.
API : Application Program Interface
Broad network access : Users can access the services by using standard platforms (such as desktop, laptop, and mobile).
Resource pooling: It allows cloud providers to pool large-scale IT resources to serve multiple cloud consumers.
Resource pooling is that through modern scalable systems involved in cloud computing and software as a service (SaaS), providers can create a sense of infinite or immediately available resources by controlling resource adjustments at a meta level. This allows customers to change their levels of service at will without being subject to any of the limitations of physical or virtual resources.
Rapid elasticity : Rapid elasticity allows users to automatically request additional space in the cloud or other types of services.
It typically done in two ways;
Horizontal Scalability : Adding or removing nodes, servers or instances to or from a pool like a cluster or farm.
Vertical Scalability : Adding or removing resources to an existing node, server or instance to increase the capacity of the node, server or instance.
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 can be monitored, controlled and reported, providing transparency for the provider and consumer.
Example : AWS Elastic Beanstalk, Windows Azure, Heroku, Force.com, Google App Engine, Apache Stratos.
IAAS : Infrastructure As A Service
IaaS is a form of cloud computing that provides virtualized computing resources over the internet. In this model cloud provider hosts the infrastructure components traditionally present in an on-premises data center, including servers, storage and networking hardware, as well as the virtualization or hypervisor layer.
The IaaS provider also supplies a range of services to accompany those infrastructure components.
Characteristics :
SCALING : This important characteristic of IaaS is called dynamic scaling — if customers wind up needing more resources than expected, they can get them immediately . A provider or creator of IaaS typically optimizes the environment so that the hardware, the operating system, and automation can support a huge number of workloads.
SERVICE LEVELS : A typical service-level agreement states what the provider has agreed to deliver in terms of availability and response to demand. The service level might, for example, specify that the resources will be available (11) 99.999% of the time and that more resources will be provided dynamically if greater than 80% of any given resource is being used.
RENTAL MODEL : IT infrastructure components are rented for a fee based on the quantity of resources used and how long they’re in use.
Within a private IaaS model, renting takes on a different focus. Although you might not charge each user to access a resource, in the charge-back model, you can allocate usage fees to an individual department based on usage over a week, month, or year. Because of the flexibility of the IaaS model, you can charge more of the budget to heavy users.
LICENSING : The use of public IaaS has led to innovation in licensing and payment models for software you want to run in these cloud environments. Another option is called “pay as you go” (PAYG), which generally integrates the software licenses with the on-demand infrastructure services.
COSTS : As per uses. Ideally, the IaaS provider will have a transparent process for identifying charges incurred by the user.
Advantages : Dynamically choose a CPU, memory, and storage configuration to suit your needs.
Access to vast computing power available on IaaS cloud platform.
Eliminates the need for investment in rarely used IT hardware.
Disadvantages : IaaS platform model is dependent on internet availability.
Dependence on the availability of virtualization services.
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