Cloud computing is a variety of computing concepts that involve a large number of computers connected through a real-time communication network such as the Internet. In science, cloud computing is a synonym for distributed computing over a network, and means the ability to run a program or application on many connected computers at the same time.

Cloud computing is most commonly deployed as either private clouds, public clouds, or a combination of the two. This deployment can be done in the cloud servers.

Cloud Servers:

Cloud servers work in the same way as physical servers but the functions provided can be different. When opting for cloud hosting, clients are renting virtual server space rather than renting or purchasing physical servers. Clients are often paid for by the hour depending on the capacity required at any particular time.

Two types of Cloud server hosting:

• Shared hosting
• Dedicated hosting

Shared hosting is the easy option whereby servers are shared between the multiple clients. Having said one shared server will have hosted many websites for many clients. This has several disadvantages including the fact that the setup is not flexible and cannot maintain with a huge volume of traffic.

Dedicated hosting is a much more advanced form of hosting, whereby clients purchase whole physical servers. This means the entire server is dedicated to them with no other clients sharing it. In some instances the client may utilize multiple servers which are all dedicated to their use. Dedicated servers allow for full control over hosting. Resource can be scaled up or scaled down accordingly, making it more flexible and, therefore, more cost-effective. When there is more demand placed on the servers, capacity can be automatically increased to match that demand without this needing to be paid for on a permanent basis. This is akin to a heating bill; you access what you need, when you need it, and then only pay for what you’ve used afterwards.

Below are the Cloud Computing Deployment Models / Cloud services.

1.    Public Cloud
2.    Private Cloud
3.    Community Cloud
4.    Hybrid Cloud

Public clouds are hosted by a third party data center located off premise at multiple locations outside of an organization’s building.  Public clouds are often hosted on virtualized multi-tenancy datacenters where different organizations have access to shared pooled hardware and power resources, yet can run their applications and data in secure, isolated environments.  These organizations can access server availability and their software applications from these offsite third party datacenters via a secure connection to their organization’s location.  Also, certain software companies now make their applications available as a service hosted from their own back-end servers.  These services can be easily deployed by an IT administrator to clients such as notebooks, desktops and mobile devices.  The software companies automatically push down updates to the clients, and as a result free up an IT administrator’s time from having to manually manage the updates.

Features and Benefits:

• Reliability – Total number of servers and networks involved in creating a public cloud and the redundancy configurations mean that should one physical component fail, the cloud service would still run unaffected on the remaining components. Where some cases clouds draw resource from multiple datacenters, an entire data-center could go offline and individual cloud services would suffer no hard effect. In other words, no single point of failure which would make a public cloud service vulnerable.

• Flexibility – There are many of IaaS, PaaS and SaaS services available on the market which follow the public cloud model and that are ready to be accessed as a service from any internet enabled device. These services can fulfill most computing requirements and can deliver their benefits to private and enterprise clients equally. Businesses can even integrate their public cloud services with private clouds, where they need to perform sensitive business functions, to create hybrid clouds.

• Ultimate scalability – Cloud resources are available on demand from the public clouds’ vast pools of resource so that the applications that run on them can respond seamlessly to fluctuations in activity.

• Utility style costing – Public cloud services often employ a pay-as-you-go charging model whereby the consumer will be able to access the resource when they need it, and then only pay for what they use.

• Cost effective – Public clouds bring together greater levels of resource and it can benefit from the largest economies of scale. The centralized operation and management of the underlying resources is shared across all of the subsequent cloud services components, such as servers, require less customized configuration. This can help in bigger market propositions to the client, relying on advertising for their revenue.

• Location independence – Availability of public cloud services through an internet connection ensures that the services are available wherever the client is located. This provides invaluable opportunities to enterprise such as remote access to IT infrastructure or online document collaboration from multiple locations.

Private clouds are typically deployed within an organization’s own internal ecosystem, often leveraging the organization’s own private data-center.  Data-centers can be virtualized to create more efficient server availability, and applications can be installed on internal virtualized servers and made accessible using the organization’s intranet.  Private clouds typically rely on the organization having trained IT staff onsite to manage the private cloud ecosystem.

Features and Benefits:

• Cloud bursting – Cloud service providers may offer the opportunity to employ cloud bursting, within a private cloud offering, in the event of spikes in demand. Private cloud service allows the provider to switch certain non-sensitive functions to a public cloud to free up more space in the private cloud for the sensitive functions that require it. Private clouds can even be integrated with public cloud services to form hybrid clouds where non-sensitive functions are always allocated to the public cloud to maximize the efficiencies on offer.

• More control – Private cloud is only accessible by a single organization, that organization will have the ability to configure and manage it in line with their needs to achieve a tailored network solution.

• Improved reliability – Where resources (servers, networks etc.) are hosted internally, the creation of virtualized operating environments means that the network is more resilient to individual failures across the physical infrastructure. Virtual partitions means pull their resource from the remaining unaffected servers. Additionally the cloud is hosted with a third party, the organization can still benefit from the physical security afforded to infrastructure hosted within data centres.

• Higher security and Privacy – Public clouds services can implement a certain level of security but private clouds – using techniques such as distinct pools of resources with access restricted to connections made from behind one organization’s firewall, dedicated leased lines and/or on-site internal hosting – can ensure that operations are kept out of the reach of interfering eyes.

• Cost and Energy Efficiency – Private cloud model can improve the allocation of resources within an organization by ensuring that the availability of resources to individual departments (business) functions can directly and flexibly respond to their demand. They are not as cost effective as a public cloud services due to smaller economies of scale and increased management costs, they do make more efficient use of the computing resource than normal LANs as they minimize the investment into unused capacity. Not only does this provide a cost saving but it can reduce an organization’s carbon footprint also.

Community Cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, or compliance considerations).

Features and Benefits:

• Reliability – It may be managed by the organizations or a third party and may exist on-premises or off-premises.

• Cost Effectiveness – The costs are spread over fewer users than a public cloud (but more than a private cloud).

Hybrid clouds are a combination of using some services delivered via a private cloud internally and other services delivered via a public cloud externally.  For example, an organization may choose to run an ERP system from their private cloud, and utilize a public cloud for offsite backup and disaster recovery purposes.

Hybrid cloud models can be implemented in a number of ways:
•    Separate cloud providers team up to provide both private and public services as an integrated service
•    Individual cloud providers offer a complete hybrid package
•    Organizations who manage their private clouds themselves sign up to a public cloud service which they then integrate into their infrastructure.

Features and Benefits:

• Scalability – While private clouds do offer a certain level of scalability depending on their configurations (whether they are hosted internally or externally for example), public cloud services will offer scalability with fewer boundaries because resource is pulled from the larger cloud infrastructure. By moving as many non-sensitive functions as possible to the public cloud it allows an organization to benefit from public cloud scalability whilst reducing the demands on a private cloud.

• Cost Efficiencies – Public clouds are likely to offer more significant economies of scale and so greater cost efficiencies, than private clouds. Hybrid clouds therefore allow organizations to access these savings for as many business functions as possible whilst still keeping sensitive operations secure.

• Security  – Private cloud element of the hybrid cloud model not only provides the security where it is needed for sensitive operations but can also satisfy regulatory requirements for data handling and storage where it is applicable

• Flexibility –  Availability of both secure resource and scalable cost effective public resource can provide organizations with more opportunities to explore different ways of operational.