Virtual Desktop Infrastructure

What is VDI (Virtual Desktop Infrastructure)?

Virtual desktop infrastructure is an architectural concept of installing a virtual machine such as Windows XP, Vista, Linux on hypervisor, which is located in a data center and connects remotely through a remote display protocol.

In the VDI mode, on the data center side there are basically two types of support to run multiple instances of Windows clients.

1. Used in blade workstations (PC Blade)
2. Or using virtual machines (VM)

The benefits compared to a traditional PC solution, VDI offers many advantages.

  • Centralization of data. As each work is reflected in the data center, all data and applications are grouped together making it easier for management (organization, update) and safety (backup, access policy).
  • The workstations are running on server machines much more robust. Workstations in classic mode do not have redundancy elements as can be found on servers (redundant power supply, disk RAID, redundant memory, etc.)
  • Customers are free from infrastructure barriers. In a VDI solution, the client device is based on I / O minimalist (keyboard, monitor, mouse) and the small software component for remote display (RDP, ICA, etc...) embedded in flash memory which allows to connect with the virtualized workstation.
  • Manageability: The VDI solution can concentrate on all the workstations in the data center. Management, updates, provisioning, backup, are therefore greatly simplified.
  • Ecology. The "green computing" is also relevant because it saves energy. A thin layer of clients consumes a very little power compared to a PC. On data center side, it is also possible to save money by using features such as VMware DPM to shut down and switch on physical servers based on the power required by virtual machines.


The disadvantages

  • The main drawback is not being able to use its position offline. While it is generally possible to use it through an Internet connection, you must at least receive an inter-connector to correct, because the high latency networks (satellite, mobile) can be very restrictive and impose on a highly optimized protocol. Still, it is possible to copy the virtual machine on a computer laptop, but to ensure synchronization between the VM and the data center is another problem.
  • Another disadvantage, availability. Access to the workstation depends on the availability of resources and links on the data center side interconnection. You must plan a secure architecture for high availability (HA) so it would be easy to manage VDI components of the infrastructure and network.


So why VDI? Well in most cases, the requirements are:

  • Users need to be administrators of their position
  • Local work (programs, data) of the post must be saved
  • The position must be strong (in resources) to compile
  • The item must be replaced quickly in case of a failure
  • And so on.

These requirements may represent the main differences between VDI and thin clients, including:

  • Value for money
  • The issue of application compatibility
  • Security Simplified
  • The simplified maintenance
  • Simplified backup

In a VDI environment, each user has his own workstation. Thus, it is possible to grant more rights to a user's virtual desktop as it does not affect other users. Notions of security that are applied to a terminal server are no longer necessarily needed.

There is no need to hold server side applications all together on the same machine as in terminal server environment. Sometimes application pool on a single server can interrupt the entire operation of the server. This problem is resolved in a VDI environment when it virtualizes the desktop. In addition, the Windows operating system is used as a type of client (Windows XP, Vista and Seven) contrary to the terminal server, which requires server operating systems. This optimizes the management of the farm, it centralizes confidential data in the data center to ensure the safety and it benefits from the protection of workstations.

Server side load balancing also brings the benefits in VDI environment. In a terminal server, load balancing is used to measure the server resources available only at the time of login of the user. Once connected to a server, the session can not be switched to another server that would be available in terms of resources. With mechanisms such as VMware DRS (Distributed Resource Scheduler) you can move virtual machines from one place to a different physical machine using VMware Vmotion.

On the maintenance side, it is possible to move a virtual machine from one hypervisor to another in order to perform operations without disrupting users.

Dark side of the solution, VDI requires more hardware resources to make (virtual desktops available) in a terminal server environment.