Desktop Pool deployment failure factors

 

 Have you ever been in the situation of suddenly virtual desktop deployment failure that you couldn't realize what's happening in your VDI environment and related services? As you may know, installation of most VDI solutions like VMware Horizon View's first deployment is not a complex task for an expert administrator, but understanding the cause of each issue that stops the desktop pool provisioning and in the following finding a way of troubleshooting progress is not easy at all.

 While there are many reasons to stop the VDI deployment, I want to investigate some cases of vDesktop provisioning failures and how to achieve a fast way to resolve or a method of bringing back the provisioning operation to its normal mode. Especially for an Instant Clone Desktop Pool, because of its complicated architecture in front of Full Clone type, we can experience deployment failure, and sadly it's not possible to change easily all settings of this desktop pool. Modifying the Golden Image needs to do maintenance actions and run the publish wizard, so any modification can lead to an unstable state of vDesktop generation. So let's go to check most of the situations:

1. Accounts: Generally two types of credentials are required in the construction of Instant Clone: First an account for accessing the vSphere infrastructure that can be a part of vCenter SSO or any other connected LDAP repository. The second one is a part of the AD domain account to join the OS of deployed virtual machines. Modifying each one of them in any maintenance interval without informing the VDI Admin team may lead the vDesktop deployment to stop: VM deployment failure (vCenter account) or VDI error (AD account).
2. Directories: Renaming the VM Folder or changing its hierarchy can cause to loss of the Reference VM and then fail the new deployment. However you can find the new placement path through Publish wizard still, it will stop the virtual desktop recover option by the way. In this situation you should know it's not possible to edit the Desktop Pool easily, thus as a good recommendation, first define the VM folder structure and precedence, then create the required desktop pools based on design. Although it's the same story for AD OU changes, it's easier to set the corresponding OU path inside the desktop pool edit section.
   
3. Privileges: There are some necessary permissions for successfully creating a Virtual Desktop. Part one: vCenter privileges on each level of vSphere's objects hierarchy for automatically virtual machine deployment inside the Cluster and put it on the corresponding VM folder. Part two: AD privileges for computer object creation inside the considered OU. Both procedures have their own required permissions. Comply these notes always: Do not modify the Horizon Connection Server considered permissions that are defined in the vSphere environment, and do not change the granted access for the VDI account that is authorized for Domain joining. It's good to create a vSphere role with the required privilege to grant required permissions to Horizon Service Account. For AD accounts, do not set a higher administrator level than is required. I think it's enough to delegate the control with the required AD permission for the mentioned account at the corresponding OU level.
   
4. Defined Assets: If you change some primary vSphere components that are selected as part of Instant Clone desktop deployment, like the Cluster and Shared Datastores, this action may break the line of new vDesktop generation without the possibility of knowing exactly what's happened. Of course, you can investigate inside the Horizon details logs to know what's going on, like checking this path (C:\Program Files\VMware\VMware View\Server\Broker\Logs) but it's a complicated and time-consuming troubleshooting operation. So as a good recommendation, define a naming pattern for each type of the vSphere object and configure them all, before running the VDI construction.
5. Name Resolution: Whenever you are using FQDN instead of IP address, changing the naming convention method or each of the VDI-related DNS records may lead Connection Server, Domain Controller, Event Database Server, and vCenter Server lost each other. The best practices of this section told us to define all servers preferably by their DNS names. For example, it's not possible to change the defined vCenter Server while there is just a related desktop pool (it means never!). Now if you decide to change the network subnets, it's enough to update the DNS cache to resolve the vCenter Server address. However be careful if you define an Alias name or CNAME record for the Horizon Server definition, never wiped them.

 In this post, I tried to mention some of the most potential failure factors. However, there are a lot of reasons for the vDesktop provisioning failure that you may encounter with them in future, like virtual machine snapshot issues (I think I should speak about them in another post). Before starting the VDI project it's highly recommended to construct the server and datacenter virtualization infrastructure carefully, with the power of scalability to avoid unnecessary changes, especially object renaming or changing directory patterns and so on.