WHAT IS 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.

Private cloud refers to a model of cloud computing where IT services are provisioned over private IT infrastructure for the dedicated use of a single organization. A private cloud is usually managed via internal resources.

The terms private cloud and virtual private cloud (VPC) are often used interchangeably. Technically speaking, a VPC is a private cloud using a third-party cloud provider's infrastructure, while a private cloud is implemented over internal infrastructure.
Private clouds may also be referred to as enterprise clouds. 

A virtual private cloud (VPC) is an on-demand configurable pool of shared computing resources allocated within a public cloud environment, providing a certain level of isolation between the different organizations (denoted as users hereafter) using the resources. The isolation between one VPC user and all other users of the same cloud (other VPC users as well as other public cloud users) is achieved normally through allocation of a private IP subnet and a virtual communication construct (such as a VLAN or a set of encrypted communication channels) per user. In a VPC, the previously described mechanism, providing isolation within the cloud, is accompanied with a VPN function (again, allocated per VPC user) that secures, by means of authentication and encryption, the remote access of the organization to its VPC cloud resources. With the introduction of the described isolation levels, an organization using this service is in effect working on a 'virtually private' cloud (that is, as if the cloud infrastructure is not shared with other users), and hence the name VPC.

VPC is most commonly used in the context of cloud infrastructure as a service. In this context, the infrastructure provider, providing the underlying public cloud infrastructure, and the provider realizing the VPC service over this infrastructure, may be different vendors.

Techopedia explains Private Cloud

There is some controversy around the very idea of a private cloud. The central idea of cloud computing is an organization should not need to build out and manage computing infrastructure itself. By utilizing cloud vendors, an organization should lower costs while receiving services and applications that are on par or better than what could be done in-house. Given this, a private cloud would seem to be going backwards. An organization would still need to build out and manage the private cloud infrastructure and not get any benefits from the economies of scale that should come with cloud computing.

The flip side of this argument is that not all organizations can give up control to third-party vendors. A proponent of private clouds would argue there are still significant benefits to private clouds in the sense that a private cloud is a way to centralize large installations of IT infrastructure in a highly virtualized manner while avoiding exposure to the unknowns of an outside cloud vendor.

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 organisation, therefore providing that organisation with greater control and privacy.


Features and Benefits of Private Clouds:

1. HIGHER SECURITY AND PRIVACY
   While public cloud services offer a certain level of security, private clouds are the more secure option. This is achieved using distinct pools of resource with access restricted to connections made from one organisation’s firewall, dedicated leased lines and on-site internal hosting
2. MORE CONTROL
    As a private cloud is only accessible by a single organisation, that organisation will have the ability to configure and manage it inline with their needs to achieve a tailored network solution
3. COST AND ENERGY EFFICIENCY
    Implementing a private cloud model can improve the allocation of resources within an organisation by ensuring that the availability of resources to individual departments/business functions can directly and flexibly respond to their demand. They make more efficient use of the computing resource than traditional LANs and can also reduce an organisation’s carbon footprint
4. 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
5. 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 Cloud Characteristics

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 categorised by the features that they offer to their client. Traits that characterise private clouds include:

• Ring fencing of a cloud which has multiple clients accessing virtualised services, which all draw their resource from a distinct pool of physical computing. These may be hosted internally or externally and may be accessed across private leased lines or secure encrypted connections via public networks
• Additional security, which is ideal for enterprises that need to store and process private data or carry out sensitive tasks. For example, a private cloud service could be utilised by a financial company that is required to store sensitive data internally and who will still want to benefit from some of the advantages of cloud computing, such as on-demand resource allocation