1.3 LAYERS AND TYPES OF CLOUDS

Cloud computing services are divided into three classes, according to the abstraction level of the capability provided and the service model of providers, namely:

(1) Infrastructure as a Service,

(2) Platform as a Service, and

(3) Software as a Service.

Figure 1.3 depicts the layered organization of the cloud stack from physical infrastructure to applications.

These abstraction levels can also be viewed as a layered architecture where services of a higher layer can be composed from services of the underlying layer

A core middleware manages physical resources and the VMs deployed on top of them; in addition, it provides the required features (e.g., accounting and billing) to offer multi-tenant pay-as-you-go services.

Cloud development environments are built on top of infrastructure services to offer application development and deployment capabilities; in this level, various programming models, libraries, APIs, and mashup editors enable the creation of a range of business, Web, and scientific applications. Once deployed in the cloud, these applications can be consumed by end users.

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2.1 VIRTUAL MACHINES PROVISIONING AND MANAGEABILITY

In this section, we will have an overview on the typical life cycle of VM and its major possible states of operation, which make the management and automation of VMs in virtual and cloud environments easier than in traditional computing environments As shown in Figure above, the cycle starts by a request delivered to the IT department, stating the requirement for creating a new server for a particular service. IT administration to start seeing the servers’ resource pool, matching these resources with the requirements, and starting the provision of the needed virtual machine. Once provisioned machine started, it is ready to provide the required service according to an SLA, or a time period after which the virtual is being released.

1.2 ROOTS OF CLOUD COMPUTING

We can track the roots of clouds computing by observing the advancement of several technologies, especially in hardware (virtualization, multi-core chips), Internet technologies (Web services, service-oriented architectures, Web 2.0), distributed computing (clusters, grids), and systems management (autonomic computing, data center automation). Below Figure shows the convergence of technology fields that significantly advanced and contributed to the advent of cloud computing. . We present a closer look at the technologies that form the base of cloud computing, with the aim of providing a clearer picture of the cloud ecosystem as a whole. 1.2.1 From Mainframes to Clouds 1.2.2 SOA, Web Services, Web 2.0, and Mashups 1.2.3 Grid Computing 1.2.4 Utility Computing 1.2.5 Hardware Virtualization 1.2.6 Virtual Appliances and the Open Virtualization Format 1.2.7 Autonomic Computing ______ Cloud computing has its roots in several technologies and developments, including virtualization, gr...

2.1.1 VM Provisioning Process

Steps to Provision VM. Here, we describe the common and normal steps of provisioning a virtual server: Firstly, you need to select a server from a pool of available servers (physical servers with enough capacity) along with the appropriate OS template you need to provision the virtual machine. Secondly, you need to load the appropriate software (operating system you selected in the previous step, device drivers, middleware, and theneeded applications for the service required). Thirdly, you need to customize and configure the machine (e.g., IP address, Gateway) to configure an associated network and storage resources. Finally, the virtual server is ready to start with its newly loaded software. These are the tasks required or being performed by an IT or a data center’s specialist to provision a particular virtual machine.

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