Virtualisation - Server

Virtual Processing Software.

This category of software ranges from virtual machine (VM) software making a single system appear to be many systems, each supporting its own operating environment, to single-system image clustering software, which makes many systems appear to be a single computing resource running a single operating environment. Server virtualisation, a segment of virtual processing, is one of the most diverse and rapidly growing parts of the virtual environment today. The relevant technologies are very broad and range from hardware partitions and traditional resource management to virtual machines and virtualising within an operating system.

Server Provisioning and Management.

This software makes it possible for operators and administrators to load, manage, and operate multi-system configurations regardless of whether any of the other virtual environment software categories are present. It is a primary component of on-demand or adaptive environment approaches to application deployment.

Server Virtualisation

In essence, virtualisation is a hardware resource sharing strategy. The core advantage of implementing server virtualisation is the ability to drive higher utilisations on physical servers by sharing the use of hardware resources across several workloads, moving away from the "one application per server" approach that often characterised the use of non-virtualised servers in the past. Another advantage is the ability to isolate one workload from another, in terms of memory, data, and hard drive contents, avoiding such problems as driver conflicts when two applications are running on the same server, and to provide better security and minimise compliance issues while sharing resources across multiple workloads.

As the operational and business benefits delivered by virtualisation have been realised, implementing virtualisation has become a major initiative for organisations. There is growing recognition among customers of the need for diversity in how they virtualise or decouple the application stack from the underlying hardware. This need for diversity stems directly from the application as different applications have different requirements in terms of isolation, flexibility, and performance. Having the right virtualisation tool for the job is as critical as it is for choosing a hardware platform or vendor.

Virtual machines
A virtual machine is a collection of different solutions that virtualise below the operating system, whereby a thin layer of software enables a customer to run multiple identical or different operating systems and applications in isolation from each other. Some overhead is associated with running the virtualisation software. This overhead is negligible for many applications, but for I/O-intensive applications, it can become a significant concern.

Today there are two different types of virtual machines: software virtualised and paravirtualised.

Software Virtualisation must intercept some OS calls and service those using an emulation of underlying hardware resources, leading to higher overhead. Software virtualisation traps privileged instructions that are used by an operating system to control hardware functions and handles them through emulation. This approach is used by VMware.

Paravirtualisation is similar to pure software virtualisation, but it offers lower overhead to the guest operating system. The key difference between software virtualisation and paravirtualisation is that a paravirtualised environment mandates that the privileged instructions be replaced or trapped on a static basis, such that a specialised version of the operating system kernel must be used. This solution typically requires a kernel modification to the operating system before it can run. IDC notes that altering kernels may require some level of compliance testing to verify post-modification operation. This approach is used by Xen and the open source community.

From a pure performance perspective, paravirtualisation would offer a performance edge compared with pure software virtualisation, while from configuration and compatibility perspectives, pure software virtualisation is easier to adopt.

TCO Calculator

Use this tool can help you quickly assess potential cost savings from consolidating IT infrastructure with VMware click here