When to use local VDI vs. offline VDI

Local and offline VMs aren't the same thing. Using the right client-based desktop virtualization technology can save money and reduce management complexity.

For years, I've been writing that desktop virtualization is more than virtual desktop infrastructure. VDI is just one type of desktop virtualization in which a desktop runs as a virtual machine in a data center, and the user connects via a remote display protocol from a thin client or laptop. Desktop virtualization also includes Terminal Server, operating system streaming or client-based virtual machines.

There are differences with client-based virtual machines (VMs) as well, particularly between "local" and "offline" VDI, so differentiating these two types of client-based VMs is my topic today.

As I discussed last week, these VMs can be "bare metal" or "Type 2." They're often called "local VDI" or "offline VDI." In many cases, the two terms are used interchangeably, but they shouldn't be. In other words, local VDI and offline VDI are not the same thing!

The confusion stems from the fact that traditional VDI is built around users' VMs running on servers in the data center, which makes that kind of desktop virtualization inherently "online." An offline connection would not allow the user to connect to the data center VM.

This "online-only" aspect of traditional VDI led people to naturally play up the "offline" benefits of running a type of desktop virtualization where the VM is on the client device itself. This led to the view that there are two use cases: VDI for online and local VMs for offline.

But using local machines only for offline computing misses a big opportunity because running desktop VMs in a data center is really, really expensive. It's so expensive that it should be done only in cases where a business need requires that desktops run in the data center. Specific business needs that would require VDI include things like "eyes-only security," the ability to run "fat" three-tiered apps across slow WAN links, and the high availability and reliability you can get from running desktops in the data center.

For customers who just want to save money or who want to reduce management complexities, running a desktop in a data center is like killing an ant with a sledgehammer; technically it works, but it's overkill.

A better solution for those who want to reduce the management costs of desktops is to use a "local VDI" product, like those from MokaFive, Virtual Computer and RingCube or certain aspects of Citrix XenDesktop. Which brings us to the crux of this week's column; these local VDI solutions are wonderful -- even though you might use them in environments where users are actually online all the time.

The bottom line is that if you want a virtual desktop system that works offline, it's generally understood that you're going to use a product that lets you run VMs locally on the client device. But keep in mind that these local solutions can also be good for scenarios where users are online. If you just want VDI for the better management and lower costs, then you do not need data center-based VDI, since these local/offline solutions will be perfect for you.

ABOUT THE AUTHOR
Brian Madden is an independent industry analyst and blogger, known throughout the world as an opinionated, supertechnical desktop virtualization expert. He has written several books and more than 1,000 articles about desktop and application virtualization. Madden's blog, BrianMadden.com, receives millions of visitors per year and is a leading source for conversation, debate and discourse about the application and desktop virtualization industry. He is also the creator of BriForum, the premier independent application delivery technical conference.

This was first published in December 2010

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