Scotland's Digital Future: Scottish Public Sector Data Centre Virtualisation Guidance

Benefits of virtualisation

Virtualisation can centralise administrative tasks while improving scalability and overall hardware-resource utilisation. With virtualisation, several operating systems can be run in parallel on a single central processing unit ( CPU). Using virtualisation, an organisation can better manage updates and rapid changes to the operating system and applications without disrupting the user.

For example an organisation running standard server applications Exchange, File and Print, DNS and Active Directory etc. on 20 physical servers would normally find this can be reduced to 3 virtualisation hosts with maybe 1 or 2 servers remaining physical, this would deliver a 75% reduction in hardware and an associated saving on power, cooling costs and management costs.

• Supports Greener ICT

Migrating physical servers over to virtual machines and consolidating them onto far fewer physical servers means lowering monthly power and cooling costs in the data centre. That means far fewer servers, less networking gear, a reduced number of racks needed, all of which translates into less data centre floor space required and a positive impact on Green ICT.

• Faster server provisioning

Server virtualisation supports deploying new services as well as scaling those that already exist because of virtualisation's intrinsic ability to rapidly deploy configurations across devices and environments.

• Operational expenditure savings

Once servers are virtualised, organisations can greatly reduce the ongoing administration and management of manual, time-consuming processes by automating operations, thus resulting in lower operational expenses.

• Improved disaster recovery and increased uptime

In the event that a server fails, an administrator can move a virtual server from one physical host server to another physical host server in minutes without interruption in availability of the virtual machine at that time.

• Assists moving to cloud computing

Virtualising your servers and abstracting away the underlying hardware is the same architecture that clouds are built on. Your data can then be moved more seamlessly into other environments.

Licensing and software implications when virtualising

Licensing is an issue for server virtualisation, looking at the 2 dominant hypervisors at present vSphere from VMware and Hyper-V from Microsoft they are licensed very differently.

VMware vSphere is licensed in a per CPU socket method, meaning that for every physical CPU in a host, a license must be purchased. An unlimited number of VM's are then allowed on that host. vSphere comes in a number of different versions, as far as licensing is concerned each containing more advanced features as the cost increases, with vSphere Enterprise plus being the current highest. In addition if you run Microsoft VM's you will also need MS datacentre licenses for each vSphere host.

Microsoft Hyper-V method of licensing is based on the edition of Windows server you are running, if you are running Standard edition, one VM may be created per host, after this, all additional VM's need to be licensed on an individual guest basis. If you have the Data Centre edition of server W2012 R2 then there is no limit on the number of VM's allowed on that host.

As with other products and applications various enterprise agreements and bundles do exist for both products and vary in price.

It is worth bearing in mind that although VMware Enterprise agreements will almost always work out beneficially, Microsoft ones depend on the amount and type of licences required. A typical Windows Data Centre license can host unlimited VM's, and with the advance in server and CPU technology this would mean all but the largest deployments will only need a handful of these. Although additional System Centre with VMM (Virtual Machine Manager) licenses are required to gain the most from a Hyper-V environment. A Microsoft Enterprise agreement should be looked at with a view to the entire organisation and not just server virtualisation and take into account desktop and office licenses too.

For Linux only, or very heavily biased organisations it may well be worth considering KVM the leading Linux server virtualisation product, although this does have support for Windows VM's it is some way behind Microsoft and VMware in this area.