No advance in information technology in the past six decades has offered a greater range of quantifiable benefits than has virtualization. Many IT professionals think of virtualization in terms of virtual machines (VM) and their associated hypervisors and operating-system implementations, but that only skims the surface. An increasingly broad set of virtualization technologies, capabilities, strategies and possibilities are redefining major elements of IT in organizations everywhere.

Virtualization is technology that lets you create useful IT services using resources that are traditionally bound to hardware. It allows you to use a physical machine’s full capacity by distributing its capabilities among many users or environments.

Virtualization is the art and science of making the function of an object or resource simulated or emulated in software identical to that of the corresponding physically realized object. In other words, we use an abstraction to make software look and behave like hardware, with corresponding benefits in flexibility, cost, scalability, reliability, and often overall capability and performance, and in a broad range of applications. Virtualization, then, makes “real” that which is not, applying the flexibility and convenience of software-based capabilities and services as a transparent substitute for the same realized in hardware.

Virtualization is the process of creating a software-based, or virtual, representation of something, such as virtual applications, servers, storage and networks. It is the single most effective way to reduce IT expenses while boosting efficiency and agility for all size businesses.The server virtualization software is generally referred to as a hypervisor.

∇ Benefits of Virtualization ∇

Virtualization can increase IT agility, flexibility and scalability while creating significant cost savings. Greater workload mobility, increased performance and availability of resources, automated operations – they’re all benefits of virtualization that make IT simpler to manage and less costly to own and operate. Additional benefits include:

• Reduced capital and operating costs.
• Minimized or eliminated downtime.
• Increased IT productivity, efficiency, agility and responsiveness.
• Faster provisioning of applications and resources.
• Greater business continuity and disaster recovery.
• Simplified data centre management.
• Availability of a true Software-Defined Data Centre.

∇ Properties of Virtual Machines ∇

VMs have the following characteristics, which offer several workarounds & benefits.

♦ Partitioning

• Run multiple operating systems on one physical machine.
• Divide system resources between virtual machines.

♦ Isolation

• Provide fault and security isolation at the hardware level.
• Preserve performance with advanced resource controls.

♦ Encapsulation

• Save the entire state of a virtual machine to files.
• Move and copy virtual machines as easily as moving and copying files.

♦ Hardware Independence

• Provision or migrate any virtual machine to any physical server.

∇ Hypervisor comparisons between KVM, Xen, VMware, Hyper-V ∇

A comparison between major server virtualization software on the basis of features and hardware requirements will make it easier for IT decision makers and end users to select the best hypervisor for them.

• KVM – a Linux based open source hypervisor. First introduced into the Linux kernel in February 2007, it is now a mature hypervisor and is probably the most widely deployed open source hypervisor in an open source environment. KVM is used in products such as Redhat Enterprise Virtualization (RHEV).
• Xen – An open source hypervisor which originated in a 2003 Cambridge University research project. It runs on Linux (though being a Type 1 hypervisor, more properly one might say that its dom0 host runs on Linux, which in turn runs on Xen). It was originally supported by XenSource Inc, which was acquired by Citrix Inc in 2007.
• VMware – is not a hypervisor, but the name of a company, VMware Inc. Our experience with VMware involves its vSphere product. vSphere uses VMware’s ESXi hypervisor. VMware’s hypervisor is very mature and extremely stable.
• Hyper-V – Hyper-V is a commercial hypervisor provided by Microsoft. Whilst excellent for running Windows, being a hypervisor, it will run any operating system supported by the hardware platform.