On August 11, 12, and 13 we delivered a Ask the Architect TechTalk series focused on desktop virtualization and VDI.  The three part series focused on:

  1. Deciding between VDI and Terminal Services
  2. Designing a desktop virtualization solution with XenDesktop
  3. Migrating users from physical devices to virtual desktops

During the TechTalk webinar, we received many great questions but were unable to answer them in the time allotted. This blog post will attempt to provide those answers. But first, I wanted to let you know where you can get access to the recorded webinars and the PowerPoints.

Part I: Deciding between virtual desktops (VDI) and virtual applications (Terminal Services)

Part II: Designing a desktop virtualization solution with XenDesktop

Part III: Migrating users from physical devices to virtual desktops

And as always, you can follow me on Twitter @djfeller.  And now to the Q/A session…

Part I: Deciding Between VDI and Terminal Services:

Q: What would be your recommended platform if streaming video or audio is needed to be delivered to a structured user environment?

A:  For structured users, we typically recommend the shared, server-based desktop but you bring up an interesting design requirement.  Typically when you hear people talk about some of the value-adds with XenDesktop, the focus is on the multimedia experience.  Well, many of those multimedia optimizations are also present within XenApp.  Now, if you have used XenApp in the past, multimedia was  a little sketchy, but I encourage you to take a look again.  There have been some impressive enhancements made, which you can see as part of the XenApp MythBusters series (http://community.citrix.com/display/xa/XenApp+Myth+Busters)\\

Q: We want to get away from running around the entire building updating all of our different applications constantly. So we don’t want anything local. How do I do this?

A: For those users who require desktops, you would want to stream the entire desktop to the end point device or use a desktop appliance and connect to a hosted virtual desktop. This would eliminate the need to install items locally and allow you to manage everything centrally. 

Q: How do we prevent users from updating their streamed desktops?

A: This is a challenge for any desktop operations environment.  When users install applications onto their desktop (this could be new apps, windows updates, IE updates/plugins, etc), the support costs climb quickly because these apps have not been validated by the IT team.  With XenDesktop, we have users receive their desktop from a single streamed image.  If a users makes changes to the desktop, those changes will NOT remain with the desktop after a reboot. Rebooting the XenDesktop desktop results in a brand new, clean desktop environment. 



Part II: Designing a Virtual Desktop Solution with XenDesktop

Q: I’ve been considering VDI for a while but our branch environment only has 512kb circuits.  How could this possibly work in this environment?

A: The branch office situation will have an impact on the type of virtual desktop you can deliver.  For example, I would not recommend using a streamed desktop for those devices unless you install a local Provisioning Services server within the branch.  If that is not an option, you also have the ability to allow the branch users to utilize a hosted virtual desktop that runs within the data center. The branch office users would connect to the hosted virtual desktop over Citrix’s transport protocol, which is extremely lightweight.  The latest scalability numbers I saw were around 15kbps (average per user). This is only an average. If you are doing a lot of multimedia operations, then I would expect that number to increase, but if you are only doing textual operations that number would likely decrease. 

Q: What is best faster processors or more memory

A:  Depends on the component.  # The XenServer that delivers the hosted virtual desktops needs both in equal amounts.  If your virtual desktops are 2GB RAM, then on a 128GB XenServer you would only get about 50-60 virtual desktops (all because you will run out of RAM).  You need to select your processors so that they are fully utilized at the same time RAM is fully utilized. 

  1. XenDesktop Controller: CPU intensive during logons and hosted virtual desktop startup (RAM and Network underutilized)
  2. Provisioning Services: Network intensive. RAM is also used for file caching the vDisk images so more read requests are services by RAM instead of by disk. CPU is underutilized

Q: What’s the best way to handle printing services for mobile and remote users.

A: As we are unsure what type of printers a remote/mobile user will have mapped on their local device, it is typically best to utilize the auto-creation of the user’s printer and to use the universal print driver This allows the user to see their local printer within their hosted virtual desktop and to not be required to install the actual print driver.

Q: We package software with Wise Package Studio….what kind of support/compatibility will we get if we go to VDI

A: If you want to install the applications within the virtual desktops, the Wise packages are still viable options. However, if you are wanted to stream the applications into the desktop, then you need to create an application profile with the XenApp tools, as application streaming is different than application installing (which Wise does).

Q: Isn’t it more efficient to allow the networking devices to compress the data stream rather than utilize CPU resources?

A: In general it is.  Depending on your environment and design, there is defiantly an option to integrate a network compression solution to compress the traffic, thereby offloading these processes from the server’s CPU.  The Citrix Branch Repeater is able to do this for many different protocols, thereby helping to improve the overall user experience. 

Q: What is the best way to handle print traffic, I am thinking of things like should this be included in base build, should you use a specialist application to throttle bandwidth usage etc.

A:  XenDesktop actually contains a policy that allows you to throttle bandwidth for different types of communication, including printing.  So for slower connections, you can tighten the screws on the printing traffic so this doesn’t disrupt the user experience.

Part III: Migrating Users from Physical Desktops to Virtual Desktops

Q: What type of profiles do you recommend.

A: You will need some type of profile that is capable of storing the user personalization settings across many different devices. This means you will need a roaming profile solution as the basis of the environment.  In XenDesktop (if using pooled desktops), a user will use a different virtual desktop everyday. Also, any changes made to the actual desktop are lost upon reboot.  During logoff, we need to upload all user settings to a centralized location that all virtual desktops can access.  When the user logs back into another virtual desktop, their settings are copied from the central site to the virtual desktop, thus personalizing it.  Unfortunately, roaming profiles have their own issues/challenges that can be mitigated by using a profile management solution like the Citrix Profile Management. 


Daniel – Lead Architect – Worldwide Consulting Solutions
Follow me on Twitter: http://www.twitter.com/djfeller
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