Question: We are currently running PVD alongside UPM. From Citrix documentation, there is a recommendation to set the following value in the registry to ensure profile management is no longer controlled by PVD and instead hand over control to UPM and redirect user profile data to C:\ drive:-

This has not been set in the existing environment, instead, this value remains at 1 which suggests PVD controls profiles on the VDIs.

Despite this, we can confirm that data is being written successfully to C:\ users, away from the P: drive and is being successfully written to the UPM user store on the network.

Question: Taking this into consideration can you confirm what the requirement is here in relation to the registry value mentioned above in order to hand over control completely to UPM?

Answer: PVD is an abstraction layer which directs the user session data to PVD. However, EnableUserProfileRedirection = 0 makes sure that the User profiles are stored only to C:\Users where the profiles can be uploaded from and downloaded to. Thus the profiles are anyways written to C:\Users, however in case of EnableUserProfileRedirection=1 the profiles would also be written to the PVD creating a copy of the profiles and eating up space on the PVD.

Therefore, EnableUserProfileRedirection value 1 or 0 would still direct the profiles to C:\Users but in case of the registry value 0, it would not write the profile copy to the PVD.

Question: If there is a requirement to set EnableUserProfileRedirection = 0 , is there a means of retrospectively fixing this with existing machine catalogs by updating catalogs with the aforementioned change made in the base disk?

Answer: The possible way is to make the change on the Master Image and update the catalog though it is NOT recommended.

Question: If the above is not possible by updating the machine catalog is there a way to address the issues by making the change and then resetting PVD?

Answer: It is advisable to introduce the change to the Master image and create a new PVD Catalog.

Question: There are a number of old profiles still being held on the P: drive on our VDIs, are you aware of any potential issues holding old copies of profiles in this volume even if UPM is redirecting everything to C: ? The reason I ask is that a couple of users have reported issues attempting to open OneNote intermittently when they log in that they open a "blank" WorkBook and I have read some threads that keeping old profiles on P: can present some unpredictable results.

Answer: There could be various causes to the issue, one of them could be profile streaming as the profile is streamed in chunks and a particular application may not have been downloaded completely when clicking on by the user.
 
In addition to the above questions can you please provide answers to the following PVD questions that might help clarify the workings of this technology:-

1. Can you confirm that the C:\ drive presented inside the operating system is the "virtualized" consolidated view of the real C: drive.:

Answer: Virtualized.

2. Is this "virtualized" system drive also presented when you launch disk management i.e. are we looking at the actual system drive or the consolidated virtualized PVD version?

Answer: Yes it is virtualized.

3. Is it true to say the real (non-virtualized) C:\ drive is not accessible from the operating system whatsoever when PVD is in place?

Answer: The real C:\ is not accessible to the user through the inner-workings are managed by the Citrix driver.

4. If the answer to question 3 is TRUE, does this exclude when we UNC to that VDIs C$ from the network i.e. if we navigate remotely to MACHINENAME\C$ , is this the real C: drive we are presented with or the PVD consolidated view again?
 
Answer: We are presented with the virtualized view.

5. When using UPM with PVD are UPM writes written to the virtualized C: drive or the real system drive C:?

Answer: It depends on the registry value. In any case the Profiles are written to C:\Users from where the UPM uploads and downloads the profiles to and from, however in case of profile redirection enabled, the profiles are written to the P:\users too.

6. An observation with the existing configuration we have in place when I create a file in C:\Users\%username% this file is replicated in P:\Users\%username% . Why is information being redirected into P:\ user profile like this? is this a consequence of the fact that we have not the disabled management of PVD via the registry key EnableUserProfileRedirection ?

Answer: Yes
 
Note: It is not exactly correct to call the whole of C:\ as virtualized as it is more of a merged view that is controlled by our driver and portrayed such to the OS.

7. What registry value determines what drive letters are assigned to this UserData2.vhd? Is it the VHDMount value below?

Answer: In general v:\ or in your case f:\ drive is the UserData2.vhd which is the application partition of the PVD and is mounted to C:\ and thus the VHDMount should be set to C:\. 

So, VHDMount set to C:\  should not have any adverse effects.