In my earlier articles I went through the steps to setup Citrix Cloud environment between Citrix Cloud and your on-premise environment. One thing which has been quite clear is that there is a critical dependency on the Cloud Connector as this is where all your clients are going to communicate with. It is essentially a proxy between your on-premise environment and Citrix.
One other thing to consider if component interaction. As we all know Citrix can be a complicated beast with many different components interacting with each other constantly, if we start moving stuff to the Cloud how is that going to affect the end user experience?
Citrix recently released an article which was derived from a set of tests which were performed to see how the environment’s can scale and respond. You can find the article here: https://docs.citrix.com/content/dam/docs/en-us/citrix-cloud/downloads/xenapp-xendesktop-service-sizing-scalability.pdf
They ran through a series of tests which were run in multiple scenario’s with the StoreFront, NetScaler, Active Directory and VDA’s being hosted by the customer and the rest of the environment being managed by Citrix. The other test was run using Citrix Essentials which is hosted purely in Azure. When they mention customer managed they can be based anywhere, either in another Cloud provider, Azure for example or on-premise.
I can see many customers deciding to keep the customer managed components on-premise as Citrix is all about end user experience and if the ICA Clients are in close proximity to the NetScaler/StoreFront/VDA’s this gives the best experience as the diagram below shows
Here is a quick summary of the key takeaways of that article to keep in mind when designing a Citrix Cloud environment
A set of three 4-vCPU Cloud Connectors is recommended for sites that host no more than 5000 Workstation VDA’s. For sites hosting 2500 VDAs 2vCPU’s are recommended.
Starting 20,000 sessions to 100 Server VDA’s is 57% faster using customer-managed StoreFront compared to Citrix-Managed so try to stick to the model in the above diagram if you can for best user experience. Citrix managed StoreFront sessions experience slower load times under load as StoreFront must authenticate through the Cloud Connector to Active Directory over the WAN. See the diagram below for the response times.
Again – the advise it to keep as much interaction between your clients and the network components local as possible to maximise user experience.
StoreFront communication
Session Launch
Launching a session when the StoreFront was managed by the customer was approximately 2 seconds quicker than StoreFront managed by Citrix. 2 Seconds doesn’t so much but to users it’s an eternity. The table below shows the difference. 
Machine creation
The tests found that the creation of machines with XenDesktop Essentials MCS deployed in Azure compared to the Hypervisor being hosted on-premise was considerably slower. Creating 1000 VMs in Azure took approximately 8 hours whether on-premise it was 103 minutes.
MCS on Azure
Citrix Cloud with on-premise Hypervisor
Summary
For a while now I have been recommending to people to use the technology available to them wisely. People tend to get excited by new shiny things and decide one day “Let’s move everything to the cloud”, they tend to forget their end users are still at least 30ms away.
These tests have proven that if we keep our Hypervisor and StoreFront/NetScaler close to our users we can realise the benefits that Citrix Cloud gives us without affecting end user experience.
More in depth analysis can be found here – https://docs.citrix.com/content/dam/docs/en-us/citrix-cloud/downloads/xenapp-xendesktop-service-sizing-scalability.pdf
And thanks to LJ from Citrix to pointing me to this article 