Cloud computing is changing the IT world in a way which is unprecedented in last decade. The economy of scale and predicable performance is pushing cloud computing across the enterprises. A significant part of the cloud-computing infrastructure available in world consists of reliable services delivered through data centers such as Amazon. In principle, cloud-computing customers do not own the physical infrastructure, instead avoiding capital expenditure by renting usage from a third-party provider.

Although cloud computing is a very promising paradigm, still not every company would want to use public clouds. Especially for core applications and applications with sensitive data, enterprises lean towards private clouds.

There are many technology options available today for cloud computing.

VMware

VMware is the industry’s first cloud operating system, transforming IT infrastructures into a private cloud. High availability, performance and reliability of VMware with cost-effective solutions are special advantages for small IT environments.

VMware brings unique characteristics to cloud computing, designed to serve the needs of businesses that want production-level performance and reliability, on and off premise.

VMware vSphere: Leveraging key technology advancements found in VMware vSphere, users get the assurance that applications can be managed, moved and operated in the cloud as they do onsite. VMware vSphere aggregates and holistically manages large pools of infrastructure—processors, storage and networking as a seamless, flexible and dynamic operating environment.

VMware ESXi and VMWare Server: Besides vSphere, VMware also offers VMware ESXi, which can be used as initial virtualization platforms. Once user is convinced of the value, he can move to more robust VMware vSphere stack.

Microsoft

Microsoft's cloud offerings have the Hyper-V and the Windows Azure Platform which is a development platform for ISVs to build applications on

Hyper-V: Microsoft Hyper-V is a hypervisor based virtualization system that can be used for x64 computers. Hyper-V can be used to enable a very reliable and cost effective virtualization solution. Hyper-V supports mixed OS virtualization with Windows and Linux systems. In the latest Hyper-V Server 2008 R2 provides features like live migration and cluster shared volume support.

Windows Azure platform: Windows Azure Platform offers a flexible, familiar environment for developers to create cloud applications and services. With Windows Azure, you can shorten your time to market and adapt as demand for your service grows. The OS component of Windows Azure is what provides the plumbing for development, service hosting and service management.

Xen

Xen is an open source cloud-computing project initiated by Citrix. Main goal of the project is to build open standards for virtualization management, improve the allocation of virtual workloads including transitioning workloads between datacenters, build a virtual switch, and enable massive cloud infrastructures.

Latest offering Xen 4.0 adds significant memory and security optimizations that will drive virtualization infrastructure to an entirely new class of performance. As a result, virtualization is made suitable for all workloads, even network intensive and high performance computing applications that would have previously experienced compromised performance on any hypervisor.