Understanding Cloud Services

          Understanding Cloud Services

     Cloud Computing is a general term used to refer to the delivery of on-demand resources and services over the Internet.

     When you watch a streaming movie on Netflix, all you need is your PC's browser and an internet connection, nothing else! That's because all the movies you have available are hosted on Netflix! And Netflix provides you with this on-demand movie catalog as a service and you pay for this service.

     So when we say that a service is in the cloud it means that the production resources to provide that service are hosted by the cloud provider.

     So the cloud is a model where we consume computing resources like any other utility... Well, now you can consume computing power, servers, applications or storage space. 

     In short, all types of computing resources and all this without having the technical infrastructure that is at the cloud provider and these computing services are accessible via a wide area network such as the Internet.

     The first thing to remember about the cloud is that it is above all a business model that uses existing technologies.

     Because of the technical side, there's really nothing new, but what is new are the concepts on which this cloud model is based.

          The four essential characteristics of the cloud 

     The first characteristic is that cloud service is, first of all, an on-demand service. This means that a customer must be able to make a request for any type of resource at any time, the response from the cloud must be immediate, and all this is possible because everything is computerized in the cloud.

     The second essential characteristic is that the cloud is a measurable service, which means that both the customer and the supplier must be able to measure the use made of resources. 

     For the customer, this allows him to know what all the resources they consume are, and this is all the more important because, in the cloud model, a customer only pays for what he uses, the other strength of the cloud is that it allows the pooling of resources.

     A cloud host has huge IT resources and its resources are shared between all its customers according to demand. And all this without anyone knowing where the consumed resource is located.

     Pooling allows elasticity in cloud resources by automatically adapting resources to variations in demand.

     And the last principle of the cloud precisely resources elasticity, and the elasticity of cloud resources is the ability to dynamically allocate resources according to needs, whether upwards, downwards, permanently or temporarily, and very quickly.

     Now that you have understood what the cloud is, let's focus a little more on the services that the cloud provides, there are several types of services and these services are categorized according to the technical layer provided, there are three models of cloud use, each of these models plays a specific role.

     The IAAS (Infrastructure As A Service) corresponds to the infrastructure part of the cloud More concretely, it provides OS instances and the entire underlying infrastructure, such as servers, network or storage. 

     In the case of use, for example, a temporary VM is made available for testing or storage expansion in this model, the user or customer of the service has to manage the addition of middleware and applications and the rest is managed by the cloud provider.

     Given the use case, the target population for the IAAS is IT operators.

     The PAAS (Platform As A Service) provides, in addition to the technical infrastructure such as the IAAS, integrated software components such as middleware instances and runtime bases, e.g. application servers or databases. 

     In this model, the service user or customer has to manage the addition of the applications - this offer, therefore, allows us to focus on the development of the applications.

     Developers are therefore the target population of the PAAS In PAAS, we have for example open-shift and Windows Azure platforms. 

     Finally, SAAS (Software As A Service) provides ready-to-use applications running on the cloud provider's infrastructure and accessible via the customer's browser. 

     As a use case one has for example access to online or office messaging, of course, the end-users are the target population of SAAS. In SAAS, we have everything that is google docs or office 365.          

Hosting mode

      The cloud comes in different hosting modes, each hosting mode will have an impact on the essential characteristics of the cloud.

     First of all, there is the public cloud, which is a model where the technical infrastructure will be outsourced to a third-party provider, in which case the IT resources will be open to all and shared. This is the flagship model of the cloud and the one we have seen so far.

     Then there is the private cloud, which corresponds to a model where all resources are reserved for the exclusive use of a single company. In this case, the main limitation is the resources and means that the company will make available for its own cloud.

     The main interest of the private cloud is that it allows meeting legal constraints, security needs or simply a desire of the company to keep control of its technical infrastructure. 

     Finally, there is the hybrid cloud, which is a mix of private and public clouds, i.e. having dedicated resources internally and public resources externally. The aim is to be able to respond to occasional peaks in load.

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