Corrupt Snapshot Causing View Composer Service Crash

Error during provisioning:Unexpected VC fault from View Composer

The above error might show up in Horizon View, if you try to use a corrupt snapshot for the deployment of new VMs.

How To Identify If  A Corrupt Snapshot Is The Cause?

  • Look at the Microsoft System Event Log on your View Composer
    • You should see something like this:

      The VMware View Composer service terminated unexpectedly. M It has done this 2 time(s).  The following corrective action will be taken in 60000 milliseconds: Restart the service.


  • Search for FATAL messages in the vmware-viewcomposer.log
    • The following message will indicate a corrupt snapshot

      2015-10-06 17:52:53,956 | WFE thread 9 | FATAL | ServiceCore.WorkflowEngine.WorkflowEngine – Unexpected exception occurred.Error reading single property ‘config.hardware.device’ from managed object: snapshot-15587


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Speed Up Your Horizon View Operations

How to speed up your Horizon View operations, you might ask? Well, you don’t have to buy an all-flash storage system or beef up your ESX hosts.

VMware Horizon View Administrator has some settings on max concurrent operations with vCenter and VMware View Composer. Increasing some of those settings can decrease the time of those operations, however when decreasing those settings, you can limit the amount of IOPs pushed to your underlying storage system, too.

Screen Shot 2015-06-26 at 5.22.46 PM

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VMware Horizon 5.2: Space Reserved For Expansion Of VMs

When a new VMware Horizon Pool gets created and an error occurs while deploying the Virtual Machines, the only thing you can see under Inventory -> Pools is a small X next to the pool name.

Screen Shot 2015-04-08 at 2.40.15 PM


Once you select the pool and edit it, you can see the pool’s settings and also any errors:

Horizon View - Error During Provisioning


Error during provisioning: Datastores unable to accommodate the new virtual machine because of one or more errors. Space reserved for expansion of VMs. VMware has a great article about this error, which can be found here.

This error does only happen when creating linked clones.
Starting with Horizon View 5.2, View Administrator checks the total total used space on a datastore does not exceed the storage overcommit level you selected for the datastore.

From VMware’s knowledge base article #2047492:

How Horizon View 5.2 or later selects datastores for linked clones

Datastore selection in Horizon View is based on the virtual machine population density. An easy way to think about population density is as a ratio of the amount of used space to the total effective capacity.

The used space contains not only the amount of space that is currently occupied on disk, but also the space needed to power on the provisioned virtual machines. Horizon View makes additional adjustments to the used space calculation to make better decisions in a real Horizon View environment. The total effective capacity is the total size of the datastore multiplied by the overcommit level.
Population density is defined in this formula:

population density = virtual used space / (total datastore capacity * overcommit level)
During provisioning or rebalance operations, Horizon View selects the datastore with the least population density.

Overcommit levels are defined in this table:

Option Storage Overcommit Level
None Storage is not overcommitted.
Conservative 4 times the size of the datastore. This is the default level.
Moderate 7 times the size of the datastore.
Aggressive 15 times the size of the datastore.
Unbounded View Manager does not limit the number of linked-clone desktops that it creates based on the physical capacity of the datastore. It is up to you to calculate the space and determine that the number of virtual machines you want to place can be supported by the datastore.*

* Select Unbounded only if you manage your own linked-clone desktops.

The Storage Overcommit level can be set when you create a new pool and select the datastore. When setting Storage Overcommit to Unbounded, Horizon View will not limit the number of linked clones based on the physical capacity of the datastore.

Horizon View Storage Overcommit

Login VSI Launcher Waiting

Every now and then, I am running a couple of VDI benchmarks. Most of the time when I run a benchmark, I re-build my whole VDI environment incl. Login VSI systems on my Shuttle DS81s (I use 10 for ~100 VDI desktops). This time, I set-up 3 Login VSI Launcher VMs and 50 VDI desktops for a quick test.

When I tried to start the test, my Login VSI Launcher was stuck in the status “waiting” and I got the following error:
The current user does not have permission to enumerate and/or logoff the user sessions on the launcher



This is not the first time that I have run into this error but I always forgot how I fixed it. Well, this time, I had a couple of minutes to take a screenshot and actually write down how to fix it for the future.

In my case, my Launcher-VMs are running Windows 7 64bit. If you run any Desktop OS, you have to enable remote RPC manually via the registry on each individual VM, or you could just create a template.

I followed these steps to get it working:

  1. Open the Registry Editor and go to HKEY_LOCAL_MACHINE -> System -> CurrentControlSet -> Control -> TerminalServerScreen Shot 2015-03-30 at 5.41.36 PM
  2. Change the decimal value of AllowRemoteRPC from “0” to “1”Screen Shot 2015-03-30 at 5.41.55 PM
  3. Try to start your Login VSI workload again. For me this did the trick and it started to work.Screen Shot 2015-03-30 at 5.44.03 PM

Optimize your VMware VDI template

People who use Horizon View or plan to use it, are always looking for the perfect template configuration. We all ask ourselves, did I turn everything off, did I install all the software which my user need, did I miss some registry entry?

While going through the same thoughts, I came across the VMware OS Optimizing Tool. If you ask me, this is exactly what you need if you want to build a stella template for your Horizon View setup.

The VMware OS Optimizing Tool is for free and helps to optimize Windows 7/8/2008 and 2012. In order to run the software, you will need Windows 7/8/2008 or 2012 and .Net Framework 3.5 SP1 installed.


To get started with VMware OS Optimization Tool, download it from here and either start it on your Horizon View template or on a different machine, which can access the Horizon View template.

Once started, you can either run an Analysis of the local machine or of a remote machine:

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If you select Analyze, you have to choose the Optimization Template Name. Select the proper template, based on the OS of your template.
Next, hit the Analyze button and wait a few seconds until you receive the result of your work.

Screen Shot 2015-03-17 at 3.10.31 PM

As shown on the image above, I ran the VMware OS Optimization Tool on my Microsoft Windows 7 Enterprise template and it detected 20 un-optimized settings, as the graph in the top right corner shows.
Luckily this tool can automatically fix all u-optimized settings with a simple click on Optimize.

After you ran the optimization wizard, you can take a look under History, which shows you when an optimization task ran and you can rollback to the previous state.

Screen Shot 2015-03-17 at 3.20.39 PM

Overall, the VMware OS Optimization Tool seems like a great tool to keep in your tools repository and come in handy when building a Horizon View template. All optimization made by this tool, are based on the VMware OS Optimization Guide.