The cost of setting up a communal cloud versus individual private cloud can be cheaper due to the division of costs among all participants

The cost of setting up a communal cloud versus individual private cloud can be cheaper due to the division of costs among all participants.
? Management of the community cloud can be outsourced to a cloud provider. The advantage here is that the provider would be an impartial third party that is bound by contract and that has no preference to any of the clients involved other than what is contractually mandated.
? Tools residing in the community cloud can be used to leverage the information stored to serve consumers and the supply chain, such as return tracking and just-in-time production and distribution.
? Since it is managed by contract with an impartial third party or by one of or the combined expert of the whole community, it has the advantage of security and privacy over the public cloud.
Drawbacks of community cloud:
? Costs higher than public cloud.

2.5.4. Hybrid Cloud service
The cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds). A hybrid cloud is typically offered in one of two ways: a vendor has a private cloud and forms a partnership with a public cloud provider, or a public cloud provider forms a partnership with a vendor that provides private cloud platforms. In a hybrid cloud, an organization provides and manages some resources in-house and some out-house. Hybrid clouds 18 offer the cost and scale benefits of public clouds, while also offering the security and control of private clouds. The advantages of the hybrid cloud include:
? Reduces capital expenses as part of the organization’s infrastructure, needs are outsourced to public cloud providers.
? Improves resource allocation for temporary projects at a vastly reduced cost because the use of public cloud removes the need for investments to carry out these projects.
? Helps optimize the infrastructure spending during different stages of the application lifecycle. Public clouds can be tapped for development and testing while private clouds can be used for production. More importantly, public clouds can be used to retire applications, which may be no longer needed because of the move to SaaS, at much lower costs than dedicated on-premise infrastructure.
? Offers both the controls available in a private cloud deployment along with the ability to rapidly scale using the public cloud.
? Supplies support for cloud-bursting.
? Provides drastic improvements in the overall organizational agility, because of the ability to leverage public clouds, leading to increased opportunities.
Drawbacks of the hybrid cloud are:
? As a hybrid cloud extends the IT perimeter outside the organizational boundaries, it opens up a larger surface area for attacks with a section of the hybrid cloud infrastructure under the control of the service provider.
? An easier approach to solving the identity, needs of hybrid clouds is to extend the existing enterprise identity and access management to the public clouds. This opens up concerns about how this approach will affect the enterprise identity and its impact on the organization’s security.
? When organizations manage complex hybrid cloud environments using a management tool, either as a part of the cloud platform or as a third-party tool, organizations should consider the security implications of using such a tool. For example, the management tool should be able to handle the identity and enforce security uniformly across hybrid cloud environments.
? A hybrid cloud makes the data flow from a private environment to a public cloud much easier. There are privacy and integrity concerns associated with such data movement because the privacy controls in the public cloud environment vary significantly from the private cloud.
? There are risks associated with the security policies spanning the hybrid cloud environment such as issues with how encryption keys are managed in a public cloud compared to a pure private cloud environment.
2.2.4. Related Technologies
These technologies are the key technologies supporting the evolution and success of cloud computing, because these technologies paved the way for the platform from which cloud computing is launched. They provided the technology and infrastructure that cloud computing relies on. They also provided the theoretical and practical experiences which cloud computing capitalizes for its success and adoption in business organizations. These technologies are Grid, cluster, virtualization and SOA computing, ancestor of cloud computing.
2.6.1. Grid Computing
It is a form of distributed computing that implements a virtual supercomputer made up of a cluster of networked or internet worked computers acting in unison to perform very large tasks. Thus, grid computing offers to cloud the capabilities for resource sharing, heterogeneity and ability to decentralize resource control.
2.6.2. Computer Clusters
A cluster is a set of multiple interconnected computers. Classifying a set of computers as a cluster requires software that makes that computers work together. Couple of very reason for clustering is performance and high availability, which means a fault tolerant hardware and software configuration. Performance clustering is a natural way to add performance if one node configuration is not enough. High availability configuration adds reliability by avoiding a single point of failure. These configurations are also used together in an active cluster configuration.
2.6.3. Virtualization
Virtualization is the representation of real machine using software that provides an operating environment which can run or host a guest operating system. It is an essential technological characteristic of clouds which hides the technological complexity from the user and enables enhanced flexibility (through aggregation, routing, and translation). By creating a virtual version of a device or resource, virtualization can improve computing efficiency, reduce the need for expensive hardware and cut overall IT costs. As new innovations continue to emerge, this technology is promising to change IT infrastructure and streamline management. Virtual machines are created and managed by virtual machine monitor. More concretely, virtualization supports the following features:
Ease of use: through hiding the complexity of the infrastructure (including management, configuration etc.) virtualization can make it easier for the user to develop new applications, as well as reduces the overhead for controlling the system.
? Infrastructure independence: in principle, virtualization allows for higher interoperability by making the code platform independent.
? Flexibility and Adaptability: by exposing a virtual execution environment, the underlying infrastructure can change more flexible according to different conditions and requirements (assigning more resources, etc.).
? Location independence: services can be accessed independently of the physical location of the user and the resource.
Two basic concepts of virtualization
1. Making multiple physical resources (such as storage devices or servers) appears as a single logical resource.
2. making a single physical resource (such as a server, an operating system, an application, or storage device) appear to function as multiple logical resources

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FIGURE 2.2: VIRTUALIZATION ARCHITECTURE
Virtualization has three characteristics that make it ideal for cloud computing 20:
1. Partitioning: In virtualization, many applications and operating systems (OSes) are supported in a single physical system by partitioning (separating) the available resources.
2. Isolation: Each virtual machine is isolated from its host physical system and other virtualized machines. Because of this isolation, if one virtual instance crashes, it doesn’t affect the other virtual machines. In addition, data isn’t shared between one virtual container and another.
2.6.4. Service Oriented Architecture
SOA is a standard way for creating connections for enterprise systems. These systems offer their capabilities as services. So, service-oriented architecture and web services enables offering of cloud computing services as web services accessible via the Internet, also SOA makes it possible for cloud services to be available in multiple platforms 21.