Deployment Models

Private Cloud

A private cloud is a particular model of cloud computing that involves a distinct and secure cloud based environment in which only the specified client can operate. As with other cloud models, private clouds will provide computing power as a service within a virtualised environment using an underlying pool of physical computing resource. However, under the private cloud model, the cloud (the pool of resource) is only accessible by a single organization providing that organization with greater control and privacy.

The technical mechanisms used to provide the different services which can be classed as being private cloud services can vary considerably and so it is hard to define what constitutes a private cloud from a technical aspect. Instead such services are usually categorized by the features that they offer to their client. Traits that characterize private clouds include the ring fencing of a cloud for the sole use of one organization and higher levels of network security. They can be defined in contrast to a public cloud which has multiple clients accessing virtualised services which all draw their resource from the same pool of servers across public networks. Private cloud services draw their resource from a dsitinct pool of physical computers but these may be hosted internally or externally and may be accessed across private leased lines or secure encrypted connections via public networks.
The additional security offered by the ring fenced cloud model is ideal for any organization, including enterprise, that needs to store and process private data or carry out sensitive tasks. For example, a private cloud service could be utilized by a financial company that is required by regulation to store sensitive data internally and who will still want to benefit from some of the advantages of cloud computing within their business infrastructure, such as on demand resource allocation.
The private cloud model is closer to the more traditional model of individual local access networks (LANs) used in the past by enterprise but with the added advantages of virtualisation. The features and benefits of private clouds therefore are:
  • 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 prying eyes
  • More control; as a private cloud is only accessible by a single organization, that organization will have the ability to configure and manage it inline with their needs to achieve a tailored network solution. However, this level of control removes somes the economies of scale generated in public clouds by having centralized management of the hardware
  • Cost and energy efficiency; implementing a 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. Therefore, although 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 traditional 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 too
  • Improved reliability; even where resources (servers, networks etc.) are hosted internally, the creation of virtualised operating environments means that the network is more resilient to individual failures across the physical infrastructure. Virtual partitions can, for example, pull their resource from the remaining unaffected servers. In addition, where the cloud is hosted with a third party, the organization can still benefit from the physical security afforded to infrastructure hosted within data centers
  • Cloud bursting; some providers may offer the opportunity to employ cloud bursting, within a private cloud offering, in the event of spikes in demand. This 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.

 

Private Cloud Is Not Virtualization
Server and infrastructure virtualization are important foundations for private cloud computing. However, virtualization and virtualization management are not, by themselves, private cloud computing. Virtualization makes it easier to dynamically and granularly pool and reallocate infrastructure resources (servers, desktop, storage, networking, middleware, etc.). However, virtualization can be enabled in many ways, including virtual machines, operating systems (OSs) or middleware containers, robust OSs, storage abstraction software, grid computing software, and horizontal scaling and cluster tools.
Private cloud computing leverages some form of virtualization to create a cloud computing service. Private cloud computing is a form of cloud computing that is used by only one organization, or that ensures that an organization is completely isolated from others.

Public Cloud

The most recognizable model of cloud computing to many consumers is the public cloud model, under which cloud services are provided in a visualized environment, constructed using pooled shared physical resources, and accessible over a public network such as the internet. To some extent they can be defined in contrast to private clouds which ring-fence the pool of underlying computing resources, creating a distinct cloud platform to which only a single organization has access. Public clouds, however, provide services to multiple clients using the same shared infrastructure.
The most salient examples of cloud computing tend to fall into the public cloud model because they are, by definition, publicly available. Software as a Service (SaaS) offerings such as cloud storage and online office applications are perhaps the most familiar, but widely available Infrastructure as a Service (IaaS) and Platform as a Service (PaaS) offerings, including cloud based web hosting and development environments, can follow the model as well (although all can also exist within private clouds). Public clouds are used extensively in offerings for private individuals who are less likely to need the level of infrastructure and security offered by private clouds. However, enterprise can still utilize public clouds to make their operations significantly more efficient, for example, with the storage of non-sensitive content, online document collaboration and web-mail.
The public model offers the following features and benefits:
  • 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
  • Cost effective; public clouds bring together greater levels of resource and so 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 whilst components, such as servers, require less bespoke configuration. Some mass market propositions can even be free to the client, relying on advertising for their revenue.
  • 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 they need, when they need it, and then only pay for what they use; therefore avoiding wasted capacity
  • Reliability; the sheer 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. In some cases, where clouds draw resource from multiple data centers, an entire data center could go offline and individual cloud services would suffer no ill effect. There is, in other words, no single point of failure which would make a public cloud service vulnerable
  • Flexibility; there are a myriad 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 fulfil most computing requirements and can deliver their benefits to private and enterprise clients alike. Businesses can even integrate their public cloud services with private clouds, where they need to perform sensitive business functions, to create hybrid clouds
  • Location independence; the 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 (in case of emergencies etc) or online document collaboration from multiple locations.

Hybrid Cloud

A hybrid cloud is an integrated cloud service utilizing both private and public clouds to perform distinct functions within the same organization. All cloud computing services should offer certain efficiencies to differing degrees but public cloud services are likely to be more cost efficient and scalable than private clouds. Therefore, an organization can maximize their efficiencies by employing public cloud services for all non-sensitive operations, only relying on a private cloud where they require it and ensuring that all of their platforms are seamlessly integrated.

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
In practice, an enterprise could implement hybrid cloud hosting to host their e-commerce website within a private cloud, where it is secure and scalable, but their brochure site in a public cloud, where it is more cost effective (and security is less of a concern). Alternatively, an Infrastructure as a Service (IaaS) offering, for example, could follow the hybrid cloud model and provide a financial business with storage for client data within a private cloud, but then allow collaboration on project planning documents in the public cloud – where they can be accessed by multiple users from any convenient location.
A hybrid cloud configuration, such as hybrid hosting, can offer its users the following features:
  • Scalability; whilst 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; again public clouds are likely to offer more significant economies of scale (such as centralized management), 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; the 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; the availability of both secure resource and scalable cost effective public resource can provide organizations with more opportunities to explore different operational avenues