In some aspects, Virtual Desktop Infrastructure (VDI) takes the best of server-based computing and removes many of the drawbacks. Most people understand that the concept of VDI is using virtualization software, typically VMware Infrastructure 3 (VI3), to host instances of a desktop operating system instead of a server operating system. There is, however, more to a VDI solution than just virtualization servers and hosted operating system instances. In this article, we'll take a closer look at the components of a VDI solution and their purpose within the overall VMware VI3 environment.
The three major components of a VDI solution are:
- The virtualization servers and supporting infrastructure
- The hosted operating system instances
- The connection broker
Let's take a closer look at each of these components.
The virtualization servers and supporting infrastructures
VDI, like server virtualization in general, is most closely aligned with VMware, although in theory any server virtualization technology would work here. We'll focus our discussions here on a VMware-centered VDI solution. In this case, these would be servers running VMware ESX Server, part of VMware Virtual Infrastructure 3. These servers would be managed by a server running VMware VirtualCenter, enabling advanced features like VMotion, VMware Distributed Resource Scheduling (DRS), and VMware High Availability (HA). Of course, to leverage these features, we must also have a storage area network (SAN) and a supporting network infrastructure. In this regard, VDI implementations are much like server virtualization implementations; they both require supporting infrastructure.
In a properly configured VDI solution, organizations will be able to take full advantage of VMotion to move hosted desktops from one physical host to another without affecting the end users (this may facilitate hardware maintenance). Organizations will also use DRS (for dynamically load balancing the hosted desktops across all the available physical hosts) and HA (in the event of an unexpected host failure). VirtualCenter templates can be used to help streamline the provisioning of new hosted desktop images. Essentially, all the power of VMware products can be brought to bear in the creation, management, and utilization of desktop operating system instances (like Windows XP Professional) instead of server instances.
The hosted operating system instances
This component is pretty self-explanatory; after all, what kind of solution would VDI be without the desktops? These will typically be installations of Windows XP Professional, although Windows Vista will see greater adoption as time passes.
Although these are virtual machines, the instances of the hosted desktop operating systems must still be managed. Organizations must use existing desktop management tools, processes, and procedures to manage these virtual desktops. Where currently deployed to manage physical desktops, applications such as Microsoft System Center Configuration Manager 2007 (formerly Microsoft Systems Management Server), Altiris, LANDesk, or others can be leveraged to also manage the hosted desktops as well. In fact, the success rate of the hosted desktops may be much higher than the physical desktops due to the fact that the hosted desktops have homogenous hardware, homogenous software configurations, and can be powered on at will.
The connection broker
This is a critical part of a VDI solution, yet it's also the component that is most often overlooked. The VMware Virtual Infrastructure 3 components (ESX Server and VirtualCenter Server) provide the virtualization engine, and the hosted desktop operating system (Windows XP Professional, typically) provides the connection method (Remote Desktop), so what good is the connection broker? In small VDI deployments, where desktops are assigned to users on a 1-to-1 basis, a connection broker may not be necessary. In larger VDI deployments, a connection broker is a necessity.
The connection broker perform a number of tasks, and these tasks vary from broker to broker. At its most basic level, a connection broker is a traffic cop; it directs incoming connection requests to an available hosted desktop. Some of the common tasks that almost all brokers can perform include:
- Authenticate users and direct them (or assign them) to a hosted desktop according to a predefined policy, group membership, or other criteria
- Control the state of a hosted desktop instance (power it on, power it off, suspend it, resume it)
- Track the connection status of a hosted desktop (i.e., is someone currently logged on, or to whom has the desktop been assigned)
Some connection brokers have more functionality. For example, some connection brokers also offer SSL VPN functionality, to encapsulate the RDP traffic inside an SSL VPN. However, organizations that already possess an established remote access mechanism don't need this feature, so it's important that organizations carefully consider the features and functions of the connection broker during the selection process.
Together, these three core components--the virtualization servers and supporting infrastructure, the hosted desktops, and the connection broker--form a complete VDI solution.
In the next installment, I'll discuss the connection broker in greater detail, and we'll look at some of the features that various connection brokers offer.
Scott Lowe has had a lifelong love of computers, dating all the way back to his first computer, a Tandy TRS-80 Color Computer. He began working professionally in the technology field in 1994, and has since held the roles of an instructor, technical trainer, server/network administrator, systems engineer, IT manager, and CTO. For the last few years, Scott has worked as a senior systems engineer with a reseller, providing technology solutions to enterprise customers. Scott also runs a virtualization-centric weblog at https://blog.scottlowe.org.