Types of Virtualization and Cloud Computing and their differences focuses on the underlying technology, analyzes the perspective of resources in easy words. This article will demystify various types of Virtualization, Cloud with link to appropriate more explanatory articles published before in related articles. We hope, with this article, Types of Virtualization and Cloud Computing; a general user will be more aware of these technologies, which to most appears as buzz words.
Types of Virtualization
The term Virtualization means the creation of a virtual computational resource which normally supplied physically as a hardware platform with an operating system and a storage device or a network resource. The operating system of a computer provides a separation between the physical resources available and their use by the user, through the creation of the logical components to a higher abstraction layer. Virtualization operates a function logically similar, constructing a plurality of logical perspectives on physical resources, each of which can be used to interact with a particular user as needed. Virtualization constructs an isomorphism between the virtual and the real system.
In the perspective of resources, virtualization creates a plurality of logical subsets of the full set of available physical resources (CPU, memory, network ). The user perceives and uses only the abstractions provided by the virtualization layer, ignoring the details of the resources.
Hypervisor based virtualization and non hypervisor based virtualization
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The software component that provides the interface for the virtual machine with the platform on which it resides is called a virtual machine monitor or hypervisor. There are two basic types:
Type I Hypervisor : The hypervisor runs directly on the hardware, allowing direct control to provide virtualization capabilities. It identifies a layer of separation between the operating system and the physical platform. A good example is Microsoft Hyper-V. The hypervisor provides that the execution of various operating systems in their environments and is fully isolated. One of the partitions, must include the host operating system, specifically Windows Server 2008, which is able to create child partitions daughters with their guest operating systems. These systems are directly running on the hypervisor. Another example is the open-source Xen project, which is widely used by different service providers of cloud computing.
Type II Hypervisor : The hypervisor is running on the host operating system, which in turn lies on the physical platform. It is particularly effective in situations where user want immediate access to both the host operating system (usually the user’s desktop OS) and the guest OS. It provides all supportive services for virtualization, but relies on the host system in memory management, resource allocation, scheduling and drivers. Known examples of hypervisor in this category are VMware and VirtualBox.
There are different types of virtualization, not necessarily based on hypervisor only :
Full Virtualization : The hypervisor virtualizes completely the hardware (memory, CPU, network etc.) thereby ensuring full compatibility with any operating system that supports the virtual physical infrastructure. The guest and host systems are completely isolated. The first significant example of full virtualization is represented by the operating system IBM CP-40 developed in 1967, it was able to run multiple instances of client operating systems. The aforementioned Hyper-V, VMware and VirtualBox ensure compatibility with this type of virtualization.
Hardware Assisted Virtualization : Also known hardware virtual machine (HVM) or native virtualization. This is an approach to full virtualization in extended condition, wherein the processor provides the architectural support to facilitate the construction and the hypervisor forward calls of different guest operating system directly to the physical hardware, increasing the overall performance of the system. Xen hypervisor, VMware, VirtualBox and Hyper-V are compatible with this technology.
Paravirtualization : Hypervisor does not simulate hardware, but it presents a modified interface functionally similar to the real one. The interface takes the form of a set of APIs called Virtual Hardware API, which are designed with a view to be used by a specific virtual machine. The lack of hardware emulation results in better performance, but the guest operating systems need to be reviewed to ensure compatibility with the virtual interface, identifying less flexibility in the solution. The Xen hypervisor is compatible with this approach.
Operating system level virtualization : The solution includes a host operating system shared centrally, with a suitably modified kernel. Guest operating systems, also contain containers or virtual private servers (VPS), must necessarily be of the same type host. The features are then replicated without the need to perform cumbersome system calls between the different layers. Examples of host operating systems are compatible with this type of virtualization is used on most Linux server via the support VServer or OpenVZ and Solaris.
How Virtualization and Cloud Computing Differs
Many IT departments have introduced virtualization in a pre-existing computing environment. Server consolidation with imitation of a production environment, virtualization of networks, addition of disaster recovery options are just some of the applications taken through virtualization.
Many IT professionals recognize the benefits of virtualization, including better use of server or cost savings associated with reduced overall dimensions, but now that we are heading towards the era of cloud and a frequently asked question is: “Is virtualization and cloud are same thing? ” or “We are already implementing a high level of virtualization, do we need to turn towards private cloud?.” To answer these questions we must first ask what are the business problems that you are about to face. And with a given response but we must clear the difference between these two technologies. Virtualization and cloud computing are not the same people, approaching towards the objectives are of different perspectives and with different levels of impact on a business or result.
Virtualization in IT has the meaning of isolating the computing resources in a manner such that an object (which may be an application, an operation or a component) in a layer that can possibly be used without the concern of changes in the underlying layers. Virtualization provides shared computing resources, thus offers the opportunity to relocate and consolidate resources isolated for better use and greater efficiency.
Cloud computing is the capacity to make the resources available on request. The essence of cloud computing is rooted in the way of your approach a service. In the context of cloud computing service identifies something available on demand. So if you mean a SaaS software, which is a software whose offer is available on request. PaaS provides a runtime environment on demand and scope of this service consists of the whole set of features that are available on demand. Since this ‘space’ is available on request, a distributed application for this environment can therefore be brought to a state of execution on demand. Distributed applications in a PaaS are delivered with SaaS.
IaaS implies the ability to provision of infrastructure on demand. For professionals supply of infrastructure for the operating results in the distribution of server. And in the context of cloud computing, all servers are virtualized and distributed in the form of a virtual machine or VMS. So, IaaS is ultimately the ability to deploy virtual machines on demand. This attribute “on-demand” must not be taken for granted, it is a term with a strong meaning in cloud computing. This means high accessibility and availability at any time, allowing self-service and universal access. In order to provide a service on demand is necessary to check and measure, so that the capacity can be planned accordingly. That said, it is clear the advantage of cloud computing with respect to virtualization. The self serving is not a key component in virtualization can be implemented on the inside. In cloud computing instead the self serving it is a fundamental concept to provide the availability to a user. Virtualization is focused on virtual machines and rooted in the management of infrastructure, operations, flexibility and distribution.
Application of virtualization in cloud computing
In the context of cloud computing, virtualization is identified then as a technology to the offer the service, logically on the server with this model. The application of hardware virtualization in this area is therefore identified more effectively with the term Server Virtualization. Each environment is realized in a set of virtual machines, created through a particular form of hardware virtualization among those listed above and the corresponding hypervisor or operating system compatible with Operating system level virtualization.
There are several possible models for Server Virtualization. A classic example is one in which the virtual machines reside directly hypervisor, which may be of both types – native (Xen) or hosted (VMware) or on an operating system that supports the Operating system level virtualization (Linux with OpenVZ). The entire infrastructure including hypervisor or operating system does not necessarily lie on the physical server permanently. It can in fact be stored as an image (for example in a network SAN) and loaded on-demand when necessary. In addition, the virtual machines can be rented for a variable period, from a few hours to several months. Desktop Virtualization is the term refers to the principle of separation of a desktop environment from the physical machine remotely responsible for implementing it through a client-server model.
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