During the last Dutch Citrix User Group I had the honour to present a 15 minutes ‘pitch’ on Citrix AppDisks which is a newly introduced feature in XenDesktop 7.8. It’s Citrix’s implementation of the popular layering solutions for application distribution.
With a lot of vendors jumping on the application layering bandwagon (yes, I’m looking at you UniDesk, LWL, VMware et all) Citrix decided to add this functionality to their core product being XenApp/XenDesktop. It was named AppDisk and AppDisks provide a way to manage applications into layers being independent to your base image.
Citrix AppDisk:
The whole idea on AppDisk is that it’s integrated into the infrastructure so you don’t have to ramp up additional infrastructure to be able to deliver AppDisk. You can use any number of applications and the AppDisk can be used with multiple machines even on different OS versions, which is powered by AppDNA as you can read later on.
Obvious benefits of layering:
- Install applications (net new or updates) being independent of the base image (it being either Client OS hosted or Server OS hosted desktops). Which simplifies your application deployment strategy and limit the number of images you’d have to maintain.
- Application update windows will be massively reduced and it improves the speed of rolling out new applications or application updates.
- Enable a fallback strategy to be able to rollback to a previous version.
- Migrating your application stack to other locations just by copying the disk containing the apps.
Next step would be to go into the console and check out the ease of use of AppDisk. What will be crucial in the implementation of your layering solution will be the management of layers and their dependencies. Application layering won’t provide you with application isolation which means you need to take account for any dependencies within the application stacks.
The demo video I showed at the DuCUG (in HiRES as the projectors couldn’t handle the higher resolution):
You can see the creation of an AppDisk, the installation of WireShark including boot driver and adding the AppDisk to a delivery group.
Powered by AppDNA:
One of the big differentiators for AppDisk will be the integration with AppDNA as it provides the option to predict the interoperability with the different application stacks and the operating system(s).
With the introduction of application layering you’ll see a reduced time to deploy but some investigation upfront is still needed because application layering isn’t the same as application isolation which means that you can still have application conflicts. That’s the sweet spot for AppDNA as you’re able to scan application layers to be compatible with other layers, existing applications and operating systems.
Gotcha’s?
This all seems great but you’ll still see some gotchas when implementing application layering in general.
Most applications will have dependencies, most common and obvious are .Net, JAVA and Oracle. Is the base image compatible with that layer? Are your application layers inter-compatible?
There’s no application isolation and App-V can manage your apps outside of any layering tech, does this add to complexity? How many applications can/do you want to layer and how many applications do you want isolated?
Some of these questions are addressed with the combination of AppDisk and AppDNA, especially with the native integration with App-V. That being said, during the DuCUG Andrew Morgan announced a new initiative to get a workflow/recommendation doc/blog for Application layering so if you’re up for it feel free to reach out to him!
Kees Baggerman
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Thank you for your great article.
I want to know whether AppDisk can do OS Layering like Unidesk does.
I heard from someone who ever tried Unidesk. Unidesk is not as stable as VMware AppVolumes if combined with Citrix. So he switch to AppVolumes.
Downside of AppVolumes are only work with ESXi and can’t do OS layering
What’s your comment for pros and cons between AppDisk, Unidesk, AppVolumes.
tq
As you mentioned UniDesk can do OS layering, AppDisks and AppVolumes are pure application layering, if you’re really looking for OS layering Mirage could be a solution too. In terms of pro’s and con’s I’d recommend catching Andrew Morgan somewhere as he has an excellent presentation on this topic (it’s way too much info to discuss here)