What is the difference between VDI desktop virtualization and virtual machines

There is no question that virtualization has changed the world of computing as we know it. Server virtualization has revolutionized how enterprise organizations run business-critical workloads. Since the age of server virtualization, organizations have consolidated servers into very dense ratios on physical hardware. It has brought about new efficiencies and capabilities.

Virtualization has not stopped at the server. It has also revolutionized desktop computing. It allows providing many of the same benefits for the desktop as possible with server virtualization in management, lifecycle operations, security, and other areas. In looking at virtualization in the realm of the desktop, many different terms come up. What is the difference between VDI, desktop virtualization, and virtual machines? This comparison between the terms and technologies will detail the differences between them.

What is the difference between VDI, desktop virtualization, and virtual machines?

When considering the various technologies that comprise enterprise virtual desktops, many terms and technologies are mentioned and described, regardless of the solution used. Three of those technologies and terms include:

    • Desktop virtualization
    • Virtual Machines

Let’s define these and see how they fit in the solutions to deliver virtual desktops to end-users.

Why is understanding the differences important?

As we will see in the guide to follow, the terms listed above are all related and interconnected in the world of virtual desktops. However, understanding the different technologies is essential to know when designing, architecting, and using virtual desktops to empower remote end-users. Choosing the right technologies is extremely important in ensuring the best solutions for remote work environments.

There are different implications and dependencies assumed with each of the terms listed as organizations dive into the world of virtual desktops. Understanding what relates, how the various technologies work, and the different nuances can steer businesses in selecting the right solutions for various use cases.

Virtual Desktop Infrastructure (VDI)

The acronym VDI comes from Virtual Desktop Infrastructure. Virtual Desktop Infrastructure (VDI) is a term that describes the infrastructure dedicated to run virtual desktops in an enterprise environment. Virtual Desktop Infrastructure (VDI) uses virtual machines to provide virtual desktops to end-users connecting from many different devices. These can include PC, Mac, Linux, tablet, or mobile devices.

VMware vSphere provides a common hypervisor platform for VDI
VMware vSphere provides a common hypervisor platform for VDI

The concept of VDI is relatively simple. A user connects the VDI environment and is given a desktop by the VDI broker out of a pool of available desktops. However, to make this relatively simple concept come to life, some rather complicated software and hardware requirements need to be satisfied to provide a seamless end-user experience for effective delivery of virtual desktops to remote users.

Virtual Desktop Infrastructure (VDI) relies on a software layer that brokers the connections from end-users to the VDI environment remote to the user. It is essential to understand with VDI, the virtual environment used to carry out business-critical operations is not running locally on an end-user device. The VDI broker and virtual machines compromising the VDI environment all reside in an on-premises or cloud data center. VMware Horizon and Citrix Virtual Apps and Desktop are modern examples of VDI solutions that organizations are using today.

VMware Horizon VDI
VMware Horizon VDI

The locality of infrastructure and data in a VDI solution has many advantages in lifecycle management, performance, and security as business-critical data does not leave the confines of the sanctioned data center environment. Additionally, the virtual machine environment is adjacent to backend resources needed for business applications.

What are the benefits of Virtual Desktop Infrastructure (VDI)

Virtual Desktop Infrastructure (VDI) brings about many advantages both for organizations and end-users. What are these?

    • Work from home – VDI provides an excellent remote access platform for remote workers. With VDI solutions, remote workers can connect to remote work environments that look and feel like working on a computer in the office. VDI desktops can be customized to the needs of the specific end-user connecting.
    • Mobility – With VDI technologies, mobility is vital. No longer is a user limited to working on a PC or laptop dedicated to running business apps. With VDI, users can access their business environment from many different devices, including mobile phones, tablets, thin clients, etc.
    • Secure access – Today, cybersecurity is critical. VDI keeps business-critical, sensitive data housed in the data center where it belongs. It helps minimize the danger of data exfiltration and malicious attack from placing an infected remote workstation on the network using a VPN. By using additional security solutions such as VMware NSX-T, data can be further protected with security policies and micro-segmentation.

VMware NSX-T provides a robust micro-segmentation platform for VDI
VMware NSX-T provides a robust micro-segmentation platform for VDI

    • Central management and monitoring – With VDI, IT can manage and monitor the environment from a central location since server-side resources reside in the data center. It also helps ease the burden of troubleshooting since, generally, the IT team can quickly triage the VDI environment if there is an issue.

Types of VDI implementations

There are generally two different VDI implementations that allow organizations to effectively provide virtual desktop resources to remote employees. These include:

    • On-premises VDI
    • Cloud-based VDI

Traditionally, on-premises VDI is the more common implementation between the two different types of VDI environments. With on-premises VDI, organizations typically provision, configure and manage their own physical VDI infrastructure in an on-premises data center. What does a typical on-premises VDI implementation include?

  1. Hypervisor hosts – The hypervisor hosts are the physical server hosts that provide the virtual machines’ hardware resources. It includes compute and memory.
  2. Network gear – The network gear includes the physical network switches, physical cabling, and other network hardware required
  3. Storage – The virtual machines configured as targets for remote users require storage for provisioning. Additionally, organizations must decide how to store and maintain user data.
  4. Hypervisor software layer – Virtual Desktop Infrastructure (VDI) solutions today run on top of a hypervisor such as VMware vSphere or Citrix Hypervisor.
  5. Virtual Desktop Infrastructure (VDI) broker and other software – The VDI connection broker component of most VDI solutions perform the brokering and placement of users on the assigned VDI desktop pools
  6. Desktop operating system – Users typically connect to desktop operation system sessions which require a desktop operation system
  7. “Golden” image – This refers to the preconfigured operating system settings, applications, and other customizations specific to the needs of the users connecting to the VDI solution
  8. Cloning mechanism – VDI solutions generally work on the premise of cloning the Golden image for end-users. There are new ways of cloning desktops that drastically reduce the time required for this operation.
      1. Administrators define this operation in the type of desktop pool configured. By selecting an automated desktop pool, the VDI solution (VMware Horizon shown below) uses a virtual machine template to generate new virtual machines on which to place users.

Creating an automated desktop pool in VMware Horizon
Creating an automated desktop pool in VMware Horizon

       9. Desktop pools – The desktop pool is the group of desktop workstations used as the target for end-users connecting to the VDI environment.

10. Entitlements and assigning users to desktop pools – Users are “entitled” to the target desktop pools. The entitlement provides the permissions and assignment required so the connection broker “knows” where to place the user.

Increasingly popular today are cloud-based options for Virtual Desktop Infrastructure (VDI). Cloud SaaS VDI solutions, like other cloud SaaS solutions, such as G Suite and Microsoft Office 365, abstract the underlying hardware and physical infrastructure and allow organizations to consume the VDI solution. This abstraction enables businesses to instantly provision VDI environments without the usual complexities of purchasing, provisioning, configuring, and managing VDI infrastructure.

One of the popular offerings in this space is the Microsoft Windows Virtual Desktop solution on Azure. Windows Virtual Desktop (WVD) is a desktop and app virtualization service that runs on the Microsoft Azure cloud and is an “as-a-Service” offering that allows organizations to quickly provision a VDI environment for their users with the infrastructure residing in Microsoft Azure datacenters.

Windows Virtual Desktop provides excellent features, including:

    • Multi-session Windows 10 deployments (this is not possible with Windows 10 installed in on-premises environments)
    • Virtualize Microsoft 365 applications and have those optimized to run in the WVD environment
    • Ability to virtualize both desktops and applications
    • It allows publishing an unlimited number of host pools for remote end-users
    • You can bring your image from on-premises and run this in WVD
    • You can pick a WVD image from the Azure Gallery
    • Deploying a WVD image is quickly done from the Azure portal, PowerShell, and REST interfaces.
    • Users can be assigned to the pools of desktops configured in WVD
    • Users can connect using either the native WVD application on their devices or using the Windows Virtual Desktop HTML5 web client

As you can see below, you can start with Windows Virtual Desktop for free and with the click of a button.

Windows Virtual Desktops VDI-as-a-Service
Windows Virtual Desktops VDI-as-a-Service

VDI desktop types

With VDI, there are usually two types of desktops configured in a typical VDI environment. These include:

    • Persistent desktops
    • Non-persistent desktops

Persistent desktops have been referred to as “stateful” desktops as these are desktops customized and configured with user settings and configuration that persists between login sessions. Any changes to the configuration or settings are saved and available on the next login session. The persistent VDI configuration aligns with the experience users are accustomed to with a physical desktop working in the office.

When they log in, they see their customized configuration settings and the desktop’s personalized look and feel. This stateful behavior is generally accomplished by the VDI solution creating a one-to-one relationship between an end-user and a full virtual machine stored in the virtual environment. When organizations start out using VDI solutions, this is typically the configuration that many gravitate towards using. Today’s VDI solutions can also target physical desktops as the target for remote users. This capability allows administrators to target physical desktops in the office. It enables placing remote users on the same workstation they use when physically working from the office.

Persistent desktops are an excellent option for businesses with power users who need access to custom applications and more processing power. These may include engineers, graphic artists, developers, etc. Persistent desktops provide customized virtual machines that fit the needs of power users connecting to the remote environment.

Non-persistent desktops can be referred to as “stateless” desktops. Typically in a non-persistent desktop configuration, the desktop does not retain any settings or configuration changes made to the desktop once a user logs out. Some solutions synchronize and maintain user data when users log out of their remote desktop. These include Citrix Appsense and VMware Dynamic Environment Manager.

With non-persistent desktops, the VDI solution generally uses a cloning process to rapidly clone subsequent desktops in desktop pools using a master image. Desktop clones are provisioned to satisfy the incoming user connection requests. It provides many advantages, including management, security, and other lifecycle benefits as the image can be updated in one place. All desktops receive the changes and updates using the cloning process.

Non-persistent desktops are often used in organizations with many task workers who may perform a limited number of repetitive tasks and don’t need a customized desktop. The software needs of a standard office worker can usually be satisfied with a standard image provided using a non-persistent desktop. Non-persistent desktops also save on storage and other resources in the VDI infrastructure as these share a standard base disk that is then cloned. Users are placed on the “delta disks” of the clone. It, in turn, results in a cheaper solution when compared to persistent desktops.

VDI application publishing

Another strong use case of Virtual Desktop Infrastructure (VDI) that may not be as obvious is virtual application delivery or “app publishing.” What is virtual application delivery or app publishing? Application publishing makes an application available instead of a full desktop session. When the user launches the VDI-backed application, it looks identical to the same application loaded locally. The difference is the application is streamed across the network.

It offers many benefits in the correct use cases compared to full desktop sessions. Many, if not most, users need access to applications and not a full desktop session. The main reason a user may need to log in to a desktop is to launch applications. With application publishing using virtual application delivery, the desktop is no longer required and the user gets direct access to the application. The footprint is drastically reduced when VDI infrastructure delivers applications and not desktops, leading to much greater user density when compared to full VDI desktops.

Organizations can use a hybrid implementation between VDI-based desktops for power users and use application publishing through virtual app delivery. This combination provides power users with the desktop they need and delivers the required apps for task workers and office employees who need access to a broad set of business productivity software.

As a note, the virtual application publishing provided by VMware Horizon and others relies on the capabilities found in the Remote Desktop Services capabilities offered in Windows Server. VMware Horizon can publish the apps that are presented by the RDS environment.

Are VDI and Desktop Virtualization the same thing?

Some references to virtual desktop solutions use the terms desktop virtualization and VDI interchangeably. Are VDI and desktop virtualization the same? No, VDI is a form of desktop virtualization that uses a hypervisor running on a cluster of physical hypervisor hosts to broker and provision virtual machines for end-users connecting to the environment.

Desktop virtualization is a much broader term that includes VDI and other virtual desktop solutions such as remote desktop services (RDS). It encompasses all technologies that provide a virtual desktop by various means to end-users.

Is VDI the same as VM?

A virtual machine provides all the identical constructs as a physical machine, including a processor, memory, storage, and network. Using the hypervisor, the operating system installed in the guest virtual machine can communicate with the underlying physical hardware running on the hypervisor host as if the hardware is dedicated to the guest operating system. The guest operating system is unaware its hardware is virtualized. However, the hypervisor handles all the interactions with the physical processor, memory, and other hardware.

Do the terms VDI and VM refer to the same thing? No, VDI and VM are two closely related technologies but are not the same thing. Virtual Desktop Infrastructure (VDI) generally relies on VMs (virtual machines) to deliver desktops to remote users. A VDI broker listens for incoming connection requests. Once a connection request is received, the broker places the user on an available VM. The virtual machine is usually running a client operating system like Microsoft Windows 10. The underlying virtual machines with VDI can also run a server operating system like Windows Server 2019, publishing applications the VDI platform presents to end-users.

What is the difference between VDI and Remote Desktop?

VDI and remote desktop services (RDS) are part of the group of technologies that make up desktop virtualization. However, they are different technologies and provide virtual desktops to end-users in different ways. Remote desktop services (RDS) is a traditional solution that has long been a capability with the Windows Server operating system. It has been known in legacy versions of Windows Server as Terminal Services. Terminal Services is now known as Remote Desktop Services. Remote Desktop Services allows multiple remote users to login to the same instance of the operating system. However, each end-user who logs in gets their own desktop session.

Microsoft implemented a thin-client architecture in Windows Server software that makes this possible. Clients can access the Windows Server desktop using the Remote Desktop Protocol (RDP). RDS can provide organizations with an excellent option for remote access, especially for those already using and heavily invested in Microsoft Windows.

One downside to RDS is that multi-user sessions are only possible with the Windows Server operating system and not Windows clients such as Windows 10. Windows Virtual Desktops (WVD), described earlier, is an exception to this as it allows multi-user sessions to Windows 10 WVD targets. For on-premises RDS, this is limited to Windows Server. Certain applications may not run correctly on the Windows Server operating systems, only clients. Organizations must keep this in mind when considering RDS as an option for remote user connectivity and productivity. It may also come into play when users are accustomed to Windows 10 clients and are now placed on Windows Server to launch applications.

Is VDI the same as RDS? There are many similarities and nuances to consider between VDI and RDS. However, VDI provides multiple virtual desktops by way of numerous virtual machines. As discussed earlier, the VDI connection broker places incoming connections on assigned pools of VMs for the particular user. The VDI environment may use a cloning process to provide the needed VMs for the end-users.

An RDS server provides multiple sessions on the same virtual machine instance. Similar to VDI, RDS servers can be configured as a pool of available RDS hosts. Microsoft’s RDS infrastructure generally uses what is called the Remote Desktop Gateway and Remote Desktop Connection Broker. The Gateway allows tunneling RDP over HTTPS for additional security. The RD Connection Broker load balances users across available RDSH servers. RDS offers similar load balancing and placement features as VDI but accomplishes this with desktop sessions and not using dedicated virtual machines.

Windows Server Remote Desktop Services configuration
Windows Server Remote Desktop Services configuration

Below, we are configuring RDP to use a Remote Desktop Gateway to connect to an RDS environment.

configuring RDP to use a Remote Desktop Gateway to connect to an RDS environment

Configuring RDP to use a Remote Desktop Gateway to connect to an RDS environment

It leads to considerations for organizations on which technology makes the most sense. What factors are important? VDI is known to be one of the most demanding technologies in regards to hardware backing the solution. It demands very capable hardware, delivering high IOPs required for cloning processes and “boot storms” that may be caused when workers are logging into the VDI environment at the beginning of the day. VDI environments may require the use of all-flash storage arrays to deliver the IOPs requirements needed for acceptable performance.

Dell all-flash SAN commonly used for VDI storage backends
Dell all-flash SAN commonly used for VDI storage backends

RDSH servers are not known for the ultra levels of performance required for VDI. However, RDS has the consideration mentioned earlier regarding multi-user sessions only working on-premises with Windows Server versions. It is also important to understand with RDS that the operating system and applications are shared between connected end-users. If a user needs an isolated and customized environment, this is much more difficult to achieve with RDS than VDI. With VDI, a customized desktop image can be used for specific end-users.

What is the difference between VDI and Citrix?

Citrix is one of the best-known vendors in delivering applications to remote end-users using application virtualization. However, Citrix includes a VDI solution known as Citrix Virtual Apps and Desktop. This product was formerly known as Citrix XenDesktop. Citrix Virtual Apps and Desktop is available in different versions that offer varying levels of capabilities and functionality.

Citrix provides a well-known desktop virtualization platform
Citrix provides a well-known desktop virtualization platform

While Citrix and VDI may be used interchangeably, Citrix is simply a vendor-specific solution providing a specific offering of Virtual Desktop Infrastructure (VDI). It is essential to understand that Citrix has its own way of implementing VDI and virtual apps.

What is the difference between VPN and VDI?

Another similar acronym that may be confused with VDI is VPN. The confusion may come from VPN and VDI being both associated with remote workers and remote work productivity. What is VPN? A VPN is a virtual private network that allows a remote end-user to connect to the corporate network using a secure encrypted tunnel. VPN connections place a remote client on the corporate network so they can access business-critical resources and applications.

Windows 10 VPN settings
Windows 10 VPN settings

VPN connections typically mean that the end-user device is connecting directly to the remote resources, and the end-user is not connecting to a remote desktop for that purpose. VPNs can expose organizations to security concerns, especially since the remote client connects to the corporate network. With this being the case, any malware or other security threats on the end-user client are connected to the corporate network. Also, data exfiltration can become an issue as well.

VDI connections generally do not need or use VPN connections to establish connections to the virtual desktop pool in the VDI environment. Most VDI solutions have a means for external devices to connect from the Internet using specialized external gateway appliances without any specialized network connectivity such as a VPN connection.

Concluding Thoughts

Virtual Desktop Infrastructure (VDI) is an excellent solution providing remote end-users the ability to access business applications to carry out business-critical tasks. It allows employees to do this from desktops, laptops, tablets, and mobile devices. VDI is known for having very stringent hardware and performance requirements that can drive up the cost of implementing VDI-based solutions. However, it is a robust solution that can satisfy organizations looking to empower both power users and general office and task workers with the tools and applications needed to carry out their daily tasks.

Many other terms are often associated with VDI, including RDS, VPN, Citrix, etc. As shown in the guide, there are nuances and differences in the various terminology and how they relate to the delivery of virtual desktops. By understanding these differences, a business can choose the right solution for their particular use case.

As organizations transition to more cloud-native applications and “as-a-Service” offerings in public cloud environments, cloud-based VDI is becoming increasingly popular. It allows businesses to quickly implement and take advantage of VDI solutions to empower remote employees without being concerned with the often complex and challenging implementation of VDI from the ground up.

Virtual Desktop Infrastructure (VDI) technologies and solutions are only going to continue to improve. As remote work and hybrid work technologies have come to the fore since the onset of the global pandemic, organizations rely heavily on VDI and other powerful technologies to empower their hybrid workforce.

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