What is VDI (Virtual Desktop Infrastructure)?

  • VDI is a virtualization technology where a desktop operating system is run and managed in an on-premises or cloud data center.
  • Virtual desktops and apps are delivered over a network to endpoint devices.
  • End users access the desktops and apps as if they were running locally.
  • Virtual desktops are hosted on virtual machines (VMs), and controlled through management software.

How does VDI work?

The desktop image of the operating system runs on virtual machines (VMs) over a hypervisor and is delivered to endpoint devices (like laptops, desktops, tablets, or smartphones) over a network. Users can then use the endpoint devices to interact with the operating system and its apps.

All VDI deployments possess the following characteristics:

  • The virtual desktops operate over VMs on a centralized server.
  • Each virtual desktop has an operating system image. Typically, Microsoft Windows is used.
  • Multiple instances of the VMs can be housed on the same server within the data center, i.e., VMs are host-based.
  • To maintain access to the virtual desktops, end clients must continuously maintain contact with the centrally managed server.
  • Clients that successfully access the VDI environment connect to virtual desktops within the resource pool using the VDI’s connection broker.
  • In the meanwhile, a hypervisor creates, runs, and manages several host machine VMs which encapsulate the virtual desktop environments.

VDI ensures secure and convenient remote access for modern digital workspaces to maintain a consistent experience across different devices.

VDI Basic Components

VDI comprises servers that “host” desktop operating systems and application software inside “guest” virtual machines that are accessible from any kind of device. Thus, at its core, VDI allows hardware and software to be abstracted on both the server and client-side.


VDI uses a hypervisor to install multiple desktop operating systems as virtual machines on a server. This hypervisor, which can be either hardware-based (bare-metal) or software-based (hosted), also manages the VMs, allowing each to operate as a standalone computer with the required, virtualized hardware and software resources, e.g. applications, at its disposal.

Connection broker

The hypervisor is also responsible for brokering the connections of the client devices to the VMs on the servers. The client devices, or “virtual desktops,” connect to the server, power up a VM’s operating system, then run the necessary applications that reside within the same VM.

Operating system instances

As VMs have virtualized the hardware resources serving the operating systems and applications, the actual machines running the virtual desktops can be of any type, e.g. desktop or laptop PCs, tablets, and even mobile phones. They do not even need to meet minimal requirements for running OS and applications anymore. The savings that arise from this capability one of the selling points for VDI.

How does VDI compare with desktop virtualization?

VDI is not synonymous with desktop virtualization as a category. Desktop virtualization consists of a single desktop computer, running a single guest virtual machine. VDI, however, is an alternative to other forms of virtual desktop delivery (like hosted shared solutions that connect endpoints to a shared desktop or local desktop virtualization where desktop environment runs directly on the client). VDI removes the desktop operating system from the local computer and places it in a shared hosting environment.

Limitations of VDI

While VDI has numerous benefits, there are a few cons to take note of:

Higher initial equipment acquisition costs

Capable server hardware is expensive, and a VDI server that can handle expected workloads might require substantial investment costs in hardware and software at the outset. The costs may rise further if you add one backup server for redundancy.

Unique organizational requirements may lead to higher support costs

Expected savings in support costs may not materialize if many users require unique applications with their own personalized settings. This might make your VDI infrastructure more difficult to administer in the long run.

Higher impact of server and network downtime

Since VDI essentially means your users are working off the server, if the server and network go down, everyone gets impacted, adversely affecting operations and resulting in lower productivity.

Benefits of VDI

The following is a list of benefits that can profoundly improve your organization:

Lower administrative and support costs

Users only need access to the operating system (OS) and application images on a central VDI server. This frees up IT staff from installing OS and applications on individual machines. Time-consuming OS migrations for each piece of hardware are avoided.

Reduced equipment acquisition and upgrade costs

Only servers need to be acquired or upgraded - a wide range of supported client devices, even old ones, are able to access them. There is no need to acquire new or upgrade existing hardware regularly. Users who practice BYOD, or Bring Your Own Device, can access the VDI at any time.

Minimized impact of hardware downtime

In case of problems with client devices, there is minimal impact on user productivity, since users can always use another device with minimal system requirements. They do not have to wait for the problem with their own device to be resolved before resuming work.

Instant backup capabilities

Dependence on individual machines for storage is eliminated with VDI, reducing data risks if machines are misplaced, stolen or have hard drive failures. All core software, applications, and files are stored on remote servers making backup and restoration a straightforward process.

Understanding non-persistent vs. persistent VDI

Persistent VDI saves all the changes and is personalized, meaning that a user always logs into the same desktop image with the changes to applications and data retained.

In persistent VDIs:

  • Upon logging in the first time a user is assigned a standardized desktop from the resource pool (if there are master or “golden” images and a Hypervisor that creates and assigns desktops).
  • Whenever the user accesses the VDI environment subsequently, they will be connected to the same desktop with all changes retained even after restarting.
  • A persistent VDI implementation suits workers with fast-paced and digital workflows who can benefit from the personalization of the desktop’s virtual apps and settings. Hence, users can easily pick up from where they left off.

In contrast, non-persistent VDI deployments do not save any changes.

In non-persistent VDIs:

  • A user can be assigned to the same or to another desktop every time they log in (if there are master or “golden” images and a Hypervisor that creates and assigns desktops).
  • No changes are saved upon restarting.
  • A non-persistent VDI implementation is suited to one-off access to a virtual desktop and does not work well when users need a personal physical equivalent.

Non-persistent VDI streamlines the management of devices for workers who do not need to save anything. It also reduces costs as IT does not have to manage data centers or maintain a large number of customized OS images.

Use cases of VDI

There are compelling scenarios for using VDI. These include:

  • Healthcare settings where security and privacy are paramount. HIPAA regulations mandate strict policies when it comes to patient data. With VDI, medical professionals are limited to only viewing the records of their own patients, based on the security profiles assigned to their virtual desktops. This access is uniform across all their devices.
  • School settings where faculty and students may be issued devices during their stay in the institution. Faculty may be restricted to viewing the records of their classes and students, while students may be barred from accessing resources outside of school hours. Once faculty members or students leave the school, the virtual desktops they used are then deleted.
  • Work environments where employees need access to their applications regardless of where they are working from, for example, from home or in the field. With VDI, employees only need to bring up their virtual desktops and start using their tools, wherever they may be or regardless of the device they are using to access the network.
  • Offices and companies that make use of shift work, for example, call centers. In such an environment, shared desktops are often the rule. With VDI, employees only need to log on to an empty workstation, bring up the desktop assigned to them, and log off at the end of their shifts. The freed-up workstation is then ready for the next shift worker’s use.
  • Engineering and design companies where graphics-heavy applications are often used. Previously, expensive machines were required when it came to this type of work. Due to advances in VDI, it is now possible for this kind of work to be performed using virtual desktops. Costs are thus made more affordable.

How does Parallels RAS help with VDI?

Parallels offers diverse desktop virtualization solutions that serve organizations of all sizes. Parallels RAS offers application and desktop delivery, making VDI more intuitive and affordable and ensuring that users can access apps they need to remain productive within today’s digital workspaces. With Parallels RAS, you get the best possible VDI experience using multi-device, multi-app workflows. Its workspace gives employees secure and comprehensive access to everything they need to stay on the go and be productive from any location they desire. Parallels RAS supports multi-cloud deployments, including Microsoft Azure (Azure IaaS) and Amazon Web Services (AWS).