Server Virtualisation

Server Virtualisation buyers guide

Virtualisation is the process of creating software emulations of particular computing environments, known as virtual machines. A VM might emulate a Windows Server 2008 environment, for example. As far as an application installed into such a VM is concerned, it is interacting with hardware that is running Window Server 2008. In reality it is interacting with a software emulation, and may be sharing the hardware with other VMs that are running other operating systems.

VMs are managed by a specialised program known as a hypervisor or virtual machine monitor (VMM) which includes tools for creating and managing the VMs, or guest operating systems, that are under its control. A Type 1 or ‘bare metal’ hypervisor runs directly on the hardware, while a Type 2 hypervisor is a process that runs within a host operating system such as Microsoft Windows Server 2012 or Red Hat Enterprise Linux. Hypervisors are available for both client machines and servers.

Benefits

Virtualisation can transform the way you manage your IT and bring huge benefits, particularly for larger organisations. For a start, a single machine can handle multiple VMs, each running not only different applications but also different operating systems. Furthermore each VM can be tailored so that only those parts of the guest operating system that the application actually needs are installed. Such an installation can make far more efficient use of your hardware, bringing savings in both requirements and energy consumption.

VMs are portable, with most modern hypervisors able to move a VM from one physical installation to another with minimal interruption to the applications running within it. This is particularly useful on the server as it means that processing loads can be distributed evenly across a number of physical machines, with the hypervisor moving VMs from hardware that is under strain to installations that have spare capacity. It also means that a server can be taken down for maintenance without interrupting service, and indeed some hypervisors can move VMs automatically in the event of hardware failure.

VMs also make it easier to prepare for a disaster. You can create snapshots of a VM which can be saved to disk or even to memory stick, ready to be revived when required. Snapshots can usually be taken without disturbing the VM itself.

Virtualisation really comes into its own in combination with Cloud-based services that allow you to move VMs out to rented servers in the Cloud, or back to your own hardware as your situation changes. This allows you to farm out your hardware requirements while remaining confident that you can bring your VMs back in-house at a moment’s notice. It also allows you to rapidly expand processing capacity without having to purchase, manage and house additional hardware.

Virtualisation is particularly handy for software development. Applications can be developed and tested within a VM where a bug won’t bring down the whole machine, and the application can be tested within its target environment while you remain within your preferred working environment. Snapshots help you preserve and analyse particular instances of your application in operation.

Considerations

Virtualisation inevitably imposes an overhead in terms of processing power and memory requirements, although modern microprocessors are designed with virtualisation in mind so the difference can be negligible. Furthermore, modern hypervisors can avoid unnecessary duplication within memory so that, for example, ten installations of Windows Server may take up only a little more space than a single installation.

However hypervisors do try and balance resources between VMs, so applications that require high levels of processing power or memory are not good candidates for virtualisation. It would make little sense to run something like Adobe Photoshop, for example, from a VM.

Virtualisation brings its own licensing requirements. In addition to the hypervisor itself, you will need licences for each guest operating system and for each application instance. You also need to consider options around backup and management tools to support your chosen virtual infrastructure. This can get complicated so don’t hesitate to contact us for advice.

Recommendations

Microsoft’s virtualisation technology is called Hyper-V and is available in Type 1 form as Hyper-V Server 2012 R2, or Type 2 form as an installable role of Windows Server 2012 R2. Supported guest operating systems include Windows Server from 2000 onward, SUSE Linux Enterprise Server 10 SP3 and 11, and Red Hat Enterprise Linux from 5.2 onward. Hyper-V also comes with the 64-bit version of Windows 8 Pro, allowing you to run Windows XP onward as guest operating systems. Microsoft provides cloud-based virtualisation services through Windows Azure, while System Center Virtual Machine Manager comes as part of System Center 2012 and provides a comprehensive set of management tools.

VMware is the other major company in this field, specialising in virtualisation through its ESX and ESXi technologies. VMware vSphere is a powerful Type 1 hypervisor, while vCenter provides a comprehensive range of management tools. VMware boasts that it supports more guest operating systems than any other hypervisor, including Windows from NT 4.0 onward, desktop versions of Windows from 3.1 onward, MS-DOS 6.22, Red Hat Enterprise Linux from 2.1 onward, SUSE Linux Enterprise Desktop 10 onward, Ubuntu Linux, Novell NetWare 5 onward, Oracle Solaris and Oracle Linux, and Apple Mac OS X from version 10.6 onward.

A Gartner report published in the summer of 2013 showed VMware to be the market leader with Microsoft in second place but closing the gap. Citrix, which has products aimed more at desktop virtualisation, is losing ground, as is Red Hat with its kernel-based virtual machine (KVM) technology.

Products

Citrix XenServer

Powerful server virtualisation platform

Red Hat Enterprise Linux

Enterprise-ready open source operating system supporting desktops, servers and mainframes

VMware ThinApp

Package and run applications without installation.

VMware vCloud

VMware vCloud helps build an agile, flexible datacenter via virtualisation

VMware vFabric

Combines the Spring Java development framework with a set of application services to provide a comprehensive cloud application platform

VMware vSphere