VDI (Virtual Desktop Infrastructure)

What is VDI?

VDI (Virtual Desktop Infrastructure) describes an IT architecture in which desktop operating systems (Windows 10 and 11, occasionally Linux) run as virtual machines in the data centre and are transmitted to the device over a remote display protocol (RDP, HDX, Blast, PCoIP).

The fundamental difference from a terminal server or RDS: with VDI every user gets their own dedicated VM — with its own operating system, its own resources and, if wanted, its own administrator rights. The classic arrangement is one user to one VM.

Benefits and limits of VDI

Search for the benefits of Virtual Desktop Infrastructure and you usually get a vendor list. More useful is the honest comparison — because every advantage has a flip side.

What speaks for VDI

Data stays in the data centre. Nothing sits on the endpoint. If a laptop is lost, no company data goes with it — in regulated industries this is often the decisive argument.

Endpoints become interchangeable. With a dedicated VM in the data centre you don’t need a powerful device at the desk. Older hardware stays usable longer, thin clients become viable.

Central management. One golden image, one policy, one patch cycle — instead of hundreds of individual devices.

Full control over location. With your own data centre you decide where the data sits and who has physical access. No provider in between.

What speaks against VDI

High upfront investment. Servers, storage, network, licences — everything has to be in place before the first user works. Unlike a cloud service, you pay for peak capacity permanently.

Capacity is rigid. If the company grows, you order more. If it shrinks, the hardware stays anyway. Seasonal demand is hard to reflect.

Operations tie up people. Someone has to know the environment, monitor it, patch it and be available when it breaks — at night and at weekends too.

Latency and network are critical. Without a stable connection a virtual desktop is unusable. What is taken for granted in the office becomes a variable at home.

Terms that mean the same thing

Several spellings and a few genuine confusions circulate around VDI:

Virtual desktop infrastructure written out in full means exactly the same as the abbreviation VDI — the terms are interchangeable.

Virtual desktop interface is a common mix-up. An interface is a connection point; an infrastructure is the whole underlying setup. What people mean is almost always the latter.

Managed VDI describes a VDI environment whose operation is handled by a service provider. The technology remains VDI — only responsibility for maintenance and monitoring moves outside. It sits between running it yourself and DaaS.

Virtual infrastructure is the broader umbrella term: it also covers virtualised servers and networks, not just desktops. VDI is one part of it.

A VDI file has nothing to do with any of this — that is a virtual disk format used by VirtualBox.

The VDI architecture at a glance

Persistent vs. Non-Persistent

• Persistent VDI (Dedicated): Each VM belongs to one fixed user. Changes are retained. High storage demand (around 50 to 100 GB per user). Good for power users, developers and CAD.
• Non-Persistent VDI (Pooled): VMs are reset after sign-out. User data lives in a profile container (FSLogix). Considerably cheaper, but it needs good application delivery.

VDI (on-premises) vs DaaS (cloud)

VDI cost example (on-premises, 200 users)

A typical on-premises VDI setup for 200 persistent desktops with VMware Horizon (calculated over five years):

For comparison: AVD multi-session with autoscaling would come to around €30 to €35 per user per month for comparable workloads — considerably cheaper, but cloud rather than on-premises.

When does classic VDI still make sense today?

Strong candidates for on-premises VDI

• Air-gapped environments — defence, research, critical infrastructure
• Low latency requirements — trading, radiology with live image processing
• Data sovereignty — data may not leave your own data centre
• An existing vSphere estate — Hardware bereits abgeschrieben, Skills vorhanden
• Predictable user numbers — no need to scale quickly

VDI is no longer ideal when

• Flexible scaling is needed (seasonal or project-based)
• Remote work is the primary scenario (cloud DaaS is more efficient)
• There is no dedicated virtualisation team
• Small organisations with fewer than 100 users (the fixed costs are too high)
• GPU-intensive work that needs the latest hardware (Azure NVv4 is often more current than on-premises kit)