There are a few categories when it comes to data-center-based desktops: Virtual desktop infrastructure (VDI) means hosting desktops on virtual machines; server-based computing (SBC) means remote desktop servers; and I'd argue that we should add another -- data center physical desktops.
Data center physical desktops are simply physical PCs in the data center. The benefit is that all the ways we manage and support physical desktops outside the data center are directly applicable to this technology.
Why not VDI?
The reason I argue for data center physical desktops is that pooling and sharing resources (like with VDI or terminal services) is bad for desktops. That setup may work great for servers, but desktops are not servers and need to be considered differently. I realize that as a long-term virtualization guy, this is heresy, and I fully expect my virtualization friends to either burn me at the stake or stage an intervention to help restore me to my senses.
I fully expect my virtualization friends to either burn me at the stake or stage an intervention.
Desktops need to be a scale-out solution, not a scale-up one. Most desktop management methods work well with a small number of users and get much harder when the user count increases. Usually the biggest challenge is scaling up pools of shared resources, like keeping storage performance high as the desktop count increases. As you add more users, you need to also add more resources. One way to do this is to have dedicated physical resources for each user, guaranteeing that as you add users, you add resources.
My second reason is that the Windows operating system is designed for fairly modest but dedicated hardware. Take a look at the optimization guide for Windows from your favorite VDI vendor. It asks you to make a hundred configuration changes to Windows; you end up with a very nonstandard Windows build. And you'll notice that the majority of the changes are about minimizing the resource demands for Windows, which is really important if you have a shared pool of resources.
If you deploy data center physical desktops, each Windows instance has the dedicated hardware resources it expects. There is no need to disable a heap of services so they don't hog the Gigahertz or Gigabytes; those physical resources are dedicated to this desktop. Take the shared resource recommendations out of the optimization guides, and you are left with just optimizing Windows for remote display -- often simply cosmetic changes.
Benefits of data center physical desktops
One of the biggest frustrations of virtualization is capricious vendor support, where they refuse to support virtualizing an application. No matter how bogus this refusal is, there is still a risk to the business if software vendors withhold support. With dedicated hardware, the application can be locally installed on the physical PC; no virtualization is involved, so support is identical to a physical PC. Removing that software vendor support risk may allow some organizations to adopt data center desktops where they couldn't previously do so.
Data center physical desktops are also about having nonshared hardware, while both VDI and server-based computing use one piece of physical hardware for multiple users. But it does not require that a particular desktop be dedicated to a user; floating assignment should still work with data center physical desktops, just like VDI or SBC.
Any profile management tool that works with physical Windows instances will also work with data center physical desktops, as will any Windows and application management tool. Since the desktops are still in the data center, all the consistency and ease of control should be the same as they are for VDI. Group Policies work great and streaming virtualized applications off a file share is a breeze. Data center physical desktops could even work well with your existing desktop deployment tool. There is no hypervisor to give you template-based deployment, nor shared storage to give you disk linking, so you will manage data center physical desktops much more like physical desktops.
So what do you need to make data center physical desktops a reality? The biggest thing is to have physical desktop hardware that fits into a scale-out platform in the data center. Rackmount PCs don't work -- only 20 per rack. Blade PCs are barely better -- about 60 per rack. You need a dedicated hardware platform that delivers hundreds of dedicated PCs per rack; these will need to use a different form factor than blades, but they use shared power and network like a blade enclosure.
It's also a huge challenge to get the PC density and cost to compete with virtualization. Plus, brokers need to support physical PCs and do so with full-performance remote display protocols; this is not currently true for all desktop brokers.
If we can get some high-density desktop platforms and good support for protocols, we could see a lot more uses for dedicated hardware in the data center.