VDI: Venturing toward a virtual world

A virtualised desktop infrastructure requires solid management capabilities, including understanding capacity planning, and choosing the correct platform, host hardware, and shared storage for your business needs.

When moving to a virtualised desktop infrastructure (VDI), one of the primary areas that needs to be considered is the management of the infrastructure. This can cover anything from the process, to the management of capacity, right through to the tools used to enhance the user experience.

Once users are moved into a VDI solution where resources are shared, the importance of managing the capacity of the backend infrastructure becomes more important. When using VDI, there is the need to be acutely aware of the capacity of the hosts running the hypervisors, the shared storage, and the distance users are from the backend infrastructure. This can range from a spreadsheet that is updated manually, to a script-driven solution that is developed, or to a third-party tool.

Choosing the right platform for hosting the VDI sessions is essential.


Mark Bradley, consultant at reseller GlassHouse Technologies,

The hosts running the hypervisors will need to be monitoring processor, memory and network utilisation at the very least. By monitoring these factors, it enables understanding of the number of VDI sessions that can run per host without impacting on the user experience.

This then allows capacity management to take place at the host level, enabling a forecast of when additional hosts will need to be purchased. VDI promotes a dynamic approach when providing new users with desktop sessions, but also means that there is a need to be at least 6 to 8 weeks ahead of the curve when purchasing new hosts.

Understanding capacity management
Whilst on the subject of capacity management, a further consideration to be taken is shared storage. Whether this is fibre, iSCSI or NFS-based shared storage, there is a need to be aware of not only capacity but also performance.

Capacity management will allow the measurement of future storage needs, whilst also giving a total number of users the VDI solution can currently host. Monitoring performance is essential to ensure that the user experience is of the highest possible standard, and stays at that level.

Application estate
Understanding the application estate is an essential step in preparing to implement VDI, and is also key to its success. This will allow those in control to gauge which applications will run within the VDI sessions, and identify users who will be unhappy with a VDI session.

It will then look at increasing the flexibility of the solution by adding virtualised application streaming, and potentially highlight applications that can be decommissioned as part of the move to VDI. Once the processes have been defined for adding applications to the VDI offering, the growth of the VDI user base can continue to increase whilst giving users a dynamic work space.

Why transition?
With the growing popularity of Windows 7, many organisations are looking to VDI to smooth out the challenges of this process. With the advancing number of user profile management options that are being used in VDI solutions, this is only going to assist the transition to Windows 7-based user profiles.

With server and desktop virtualisation, the temptation is to 'scale up' with the hosts so they then have very large processor and memory capacities. The preferred option for many is the 'scale out' approach.

Two possible benefits and one negative effect of this scale out approach to VDI are:


  • Reduced impact of host failure: With more hosts, the number of VDI sessions affected by host failure is reduced.
  • Lower cost hosts: By using smaller hosts, the cost of adding an additional host is lower, and therefore an easier sell to management.
  • Increased licensing costs: Depending on the hypervisor, this approach may require more licenses for hypervisors and/or management agents.

Accurate costing is key
The cost of VDI implementation is one that, if mismanaged, can easily be the factor that affects the management's faith in it being the correct choice. Understanding the cost of all of these elements will allow accurate return on investment calculations about what the VDI solution will be able to deliver.

As well as actual costs, you will see a reduction in expenditure of the management and deployment of new desktops to users. Even with a well-developed deployment methodology for physical desktop infrastructure, this could be anything from eight hours up to one week.

VDI can reduce this down to minutes, allowing valuable desktop support engineers to concentrate on improving the desktop infrastructure rather than provisioning it for new users. Plus, by implementing VDI, the business can gain savings in power through phasing out desktops and laptops for thin clients.

Considering the points made above, it is possible to see that even before virtualisation is chosen, initial desktop decisions need to be made. Choosing the right platform for hosting the VDI sessions is essential. Pick the right host hardware, hypervisor and shared storage to suit the business needs. A tiered approach could cover the resources allocated to the VDI session or the performance of the shared storage housing the VDI files.

Mark Bradley is a consultant from reseller GlassHouse Technologies and a contributor to SearchVirtualDataCentre.co.UK.

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