In simple terms Cloud computing can be defined as on-demand computing resources- this includes applications & services to underlying Infrastructure. There are mainly three models and trends that are currently being used:
Private cloud
A private cloud or on premise cloud is a set of services for an organization that is built on shared resources (both hardware and software) and can be provisioned on need basis within a virtualized environment using an underlying pool of physical computing resource. The private cloud also provides commodification of IT services for internal customer or business verticals to shop from a menu of metered services in a virtualized environment. This eliminates the need of unnecessary hold of resources that will never be used.
Multi-tenancy architecture provides ability to serve multiple customers on a single shared instance and this is the major difference between basic virtualization and the cloud computing.
This method of virtualized computing is more economical as the maintenance cost is shared between different services and systems within an organization. Security, governance capability and controls are the major drivers for any organization to choose Private cloud in preference to Public Cloud model.
Public cloud
It is crystal clear with the term ‘ Public’ , this model of cloud is owned and operated by cloud service providers in a public yet secured domain. In the public cloud model, users do not purchase any hardware or software rather they use resource of the cloud provider on a certain cost. There are different models offered by many companies in today’s world like On-demand self-service- that provides ability to the customer to sign up and receive services without waiting for long, Network Access – this provides ability to use your end point units to access the platform, Pooling- Shared or pooled resources offering that serves multiple customers, Pay as you go or measured service which is designed for the customer to control their budget and pay only based on the usage of service. There are three broad categories of a public cloud offering.
Software as Service: In SaaS model, Customer use license application either as a service on demand using a subscription based model or as a ‘pay-as-you-go model.
Platform as Service: PaaS is another category of cloud computing that provides a stage to the developers to build applications and services over the internet that are accessible via web browser.
Infrastructure as Service: IaaS is somewhat similar to SaaS as it provide similar pay-as-you-go or subscription model but has a bigger and better coverage for end to end solution that includes software, hardware, storage, network, Datacenter and other underlying infrastructure.
Hybrid cloud
Simplified definition of Hybrid cloud is the amalgamation of private and public cloud models. This model uses functionality of both Private and Public cloud architecture to manage workloads and it provides flexibility in business continuity and disaster recovery strategic planning. Companies with compliance requirement for keeping critical or confidential data onsite can use private cloud to host their primary servers/ data on site and use public cloud to host their non-critical systems. This can also be used as a site recovery option for Tier 1 and Tier 2 systems for any organization.
Conclusion
All cloud computing models have distinct features and advantages and it is purely on the business requirement for any organization to choose the model that suits their organization strategic plans and goals. Public cloud offering is a hassle free way to manage your critical IT services specially I like its utility model (pay-as-you-go) that has no long term commitment and contracts whereas Private cloud offers more control over resources, architecture, security and compliance controls like PCI or SOX. Last but not least Hybrid provides more flexibility in terms of resource utilization, work load management and site recovery options.
Reference : Gartner, IBM and Microsoft
