Desktop virtualization comparison: VDI vs. Remote Desktop Services

For desktop virtualization, you have a choice between the paths of VDI and Remote Desktop Services. Robert Frost took the road less travelled, but you don't have to choose just one.

This article can also be found in the Premium Editorial Download: Virtual Data Center: Top desktop virtualization and DaaS strategies for the enterprise:

For desktop virtualization in your organization, you can take the VDI route or the Remote Desktop Services route...

-- or you could go with a combo.

Microsoft Remote Desktop Services (RDS), previously called Terminal Services, has been with us for 15 years. Virtual desktop infrastructure (VDI), on the other hand, is still getting its engine going in many organizations.

To help you choose the right path for your environment, see how VDI and RDS stack up against one another in this desktop virtualization comparison.

What's the difference?

Microsoft Remote Desktop Services and VDI are each suited to different scenarios.

VDI has a separate virtual machine (VM) for each user and uses a desktop operating system in that VM. It puts isolation between users, so VDI is better for highly regulated or secured environments where information disclosure is a big issue. That also means you have lots of copies of Windows to keep clean and safe. Plus, you have to deal with mass VM boots and updates, which can drain VDI storage performance.

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Of course, VDI environments don't have to be locked down. You can allow users full administration and local application install rights in their personal VM. However, this attaches the user to the specific VM and often means the VM cannot be updated using a single master image update.

RDS, on the other hand, has users sharing a VM running a server OS. That makes Microsoft Remote Desktop Services more suited to task-oriented and collaborative uses. Since there are fewer Windows instances, the storage load for updates and reboots is less. There's also less CPU and RAM overhead, so you can usually run more users per unit of hardware.

RDS environments are always locked down because they're a shared resource and need to provide a uniform level of service to every user. Microsoft Remote Desktop Services also provides high availability through clusters or farms of servers. That means RDS VMs are effectively disposable: You just need enough available for the users who are connected at any given moment. Since you don't need specific VMs to be constantly available, you don't need expensive shared storage and can place RDS VMs on local storage in the host.

As you can see from our desktop virtualization comparison, these two technologies address very different uses. So, many organizations deploy both. Different groups of users benefit from VDI and Microsoft Remote Desktop Services, as they're really complimentary solutions. To make things easier, you can use the same connection broker and the same client to run both VDI and RDS.

Where vendors can improve RDS support

To choose your desktop virtualization path, it's important to know a little more about the major vendors. There are lots of VDI offerings out there, but here's how Citrix Systems Inc. and VMware Inc. provide VDI and RDS support:

Citrix
Citrix has been doing data center-based user desktops for around 20 years and hitched onto the Windows wave nice and early. In fact, what is now called RDS was originally Citrix Multi-Win. When Microsoft first released Terminal Services as a special edition of Windows NT 4.0, it was Citrix developers that wrote the code, licensed to Microsoft.

Citrix held onto its very efficient HDX protocol, an important part of VDI. It also has Citrix Provisioning Server, which streams the OS to a VM as it boots and enables the single image OS maintenance nirvana -- and works with both RDS and VDI environments. Citrix XenApp also works with RDS and makes it a more scalable and WAN-optimized solution. Making things easier for customers that use both RDS and VDI, Citrix provides a license that covers both XenDesktop and XenApp.

I'm an old-school Citrix guy and I always used to say Citrix is very easy to do... badly. Citrix has been tarred with a lot of poor implementations, but the VDI wave allowed the company to revitalize itself.

VMware
VMware could do a much better job of supporting RDS in its View product. The ability to use View to broker and secure a connection to RDS has been available since version 3, but you won't often hear about that. The big restriction with View and RDS is the lack of VMware's PC-over-IP (PCoIP) protocol support. It only supports Microsoft's own Remote Desktop Protocol. Teradici, however, recently announced that it will add PCoIP support to Remote Desktop Session Host.

I suspect the reason is that the software PCoIP rendering engine in View is quite CPU intensive, meaning two or three PCoIP users could redline an RDS server by watching YouTube videos. Now that Teradici released its PCoIP server offload card, the Apex 2800 that removes the CPU load for the PCoIP encode, I'd love to see it used to enable PCoIP from RDS.

The other thing VMware could do to improve RDS support is bring its linked clone technology to RDS hosts. This would allow a single master image to be patched and maintained, and then you could use it to automatically update dozens of RDS VMs.

Keeping the caveats from this desktop virtualization comparison in mind, you can determine where VDI or RDS might solve problems you have in your business. Neither solution is right for all uses, and few organizations use only one approach. Both paths can help you cope with the potential end of the Windows desktop.

ABOUT THE AUTHOR:
Alastair Cooke
is a freelance trainer, consultant and blogger specializing in server and desktop virtualization. Known in Australia and New Zealand for the APAC virtualization podcast and regional community events, Cooke was awarded VMware's vExpert status for his 2010 efforts.

This was last published in July 2012

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Which is better: VDI or Remote Desktop Services?
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Remote
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I need to think about it
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Remote Desktop services
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Dont know yet.I am new
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Allow a server to host multiple, simultaneous client sessions uses Remote Desktop Services technology to allow a single session to run remotely. A user can connect to a Remote Desktop Session Host server formerly known as a terminal server by using Remote Desktop Connection client software. The Remote Desktop Web Connection extends Remote Desktop Services technology to the web
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Remote Desktop Services
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less expensive, simpler, prooven
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Client Company security requirements
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VDI + RDP services help a lot on lowest bandwidth in order to met large & mid scale org requiremnt
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Clients don't need secure separation.
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VDI supports BYOD better & uses a thinner communication protocol for overall less bandwidth. Trying to train people on 2 different desktop types if combining both technologies isn't going to work here. It has to be simple and consistent.
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We will use a combination of both in the future as our client connection needs are changing, some needing only an app others neding a desktop
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RDS is much simplier for a standard set of applications. We ahve about 300 users on 6 RDS 2008 R2 servers.
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Cheaper, faster - better!
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I would use a combination of both, because some users just need to share an application or the server resources to perform their job while others want the flexiblty to move from system to system and have their persona follow them.
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We use both Citrix XenApp and Dell vWorkspace. RDS gives many more users per server and is much more cost efficient if you do it right. VDI gives the ability for persistent desktops that can be used by those requiring the abiltiy to install and manage their own applications or OS configuration (Developers for instance). VDI nonpersistant desktops can also be useful for different baseline testing situations (and why use nonpersistent VDI sessions for general usage if you are doing RDS anyway). Dell vWorkspace costs a fraction of Citrix solution (both acquisition and maintenance) and a single console to manage both RDS and VDI and EOP protocol supports offshore usage like Citrix's HDX.
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Ease of implementation and central management
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Due to the application dependencies.
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They both have their merits. I use mostly RDS\Citrix than VDI.
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I think I might like this not that I dont
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VDI is cheaper...that's why it's better.
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