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Citrix XenDesktop 7.15 On The Latest DELL EMC vSAN Hyper Converged Infrastructure 

Citrix XenDesktop 7.15 installations - Part 2

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Welcome to part 2 in the series of Citrix XenDesktop 7.15 installations. If you have missed it you can find part 1 here where we run Citrix XenDesktop 7.15 on Nutanix NX.

Why run XenDesktop on ESXi 6.5 and vSan 6.6?

The customer requirements were to replace a XenDesktop 7.1 deployment, using traditional 3 tier storage systems. The customer was attracted to HCI for the scalability and performance it provides.

Compatibility

Citrix currently publish a nice matrix, below is a screenshot of vSphere compatibility, but a full list of hypervisors are available here.

vsphere table

Features not supported

In the previous article we mentioned several of the Citrix features that are not supported with AHV, but this is not an issue with vSphere which is what you would expect with a much more mature hypervisor.

Setting up your hosting connection

Getting started you will need to setup a hosting connection, you don’t need to install any plugins as with AHV, as this is supported out of the box.

This connection works over HTTPS so to get this to work it is always recommended you don’t use a self-signed certificate in a production environment. However, if you need to trust your certificate for setting up a hosting connection, this is now a very simple process.

  • Browse to the vSphere web client URL, you will should see an option to “Download trusted root CA certificate
  • This then downloads a cert bundle in a file called “Downloads.zip” extract the files then import the file from the “Win” Directory in to the trusted root store
  • To verify if this is working you can then browse back to your vCenter and the padlock should be displayed (assuming IE)
  • Then add your vCenter as a connection, and provision resources

Deploying and updating machines

The MCS deployment process is much the same however we find one huge issue when trying to update a machine catalogue. Creating the catalogue completes without issues and adding additional machines from the current snapshot also completes. However, when updating the machine, the VM loses its OS disk, and then won’t boot.

Disk structure pre-MCS update

pre mcs update

As you can see here we are using MCS with Cache to RAM, the 3 disks are:

  • 1
    OS Disk
  • 2
    Identity Disk
  • 3
    MCS Cache Disk

However, after running and MCS update, the disk structure is as below.

mcs test update

As you can see there are now only 2 disks:

  • 1
    Identity Disk
  • 2
    MCS Cache Disk

As part of the MCS process the OS disk is removed from the VM so if a VM is started it won’t have an OS to boot into so will try and PXE Boot.

pxe boot

There is apparently a private fix for this, and with the release of 7.16 very recently this might have been resolved  (we have not had chance to test this). It is also reported that this error goes back several versions to 7.13 (again we have not had the opportunity to test this).

With the help of several users on the Citrix forums there is a power CLI script that convert the disks to VSAN objects.

$VMs = Get-VM -Name "PREFIX*"

foreach ($VM in $VMs) {

$Datastore = Get-Datastore -VM $vm

$Datacenter = Get-Datacenter -VM $vm

$diskpath = "[" + $Datastore.Name + "] " + $vm.Name + "/"

$vmidpath = $diskpath + $vm.Name + "_IdentityDisk.vmdk"

$vmtemppath = $diskpath + $vm.Name + "_TemporaryStorage.vmdk"

$renameidSource = "vmstore:\" + $Datacenter +"\vsanDatastore\" + $vm.Name + "\" + $vm.Name + "_IdentityDiskOld.vmdk"

$renameidDestination = $vm.Name + "_IdentityDisk.vmdk"

$converthdd = $diskpath + $vm.Name + "_IdentityDiskOld"

#Convert Disk

Get-HardDisk -VM $vm | Where-Object {$_.Filename -like "*_IdentityDisk*"} | Copy-HardDisk -DestinationPath $converthdd -Confirm:$false

#Remove Disk

Get-HardDisk -VM $vm | Where-Object {$_.Filename -like "*_IdentityDisk*"} | Remove-HardDisk -DeletePermanently:$true -Confirm:$false

Get-HardDisk -VM $vm | Where-Object {$_.Filename -like "*_TemporaryStorage*"} | Remove-HardDisk -Confirm: $false

#Rename Identity Disk

rename-item $renameidSource $renameidDestination

#Add Disk

New-HardDisk -VM $vm -DiskPath $vmidpath

New-HardDisk -VM $vm -DiskPath $vmtemppath

}

Once this has been run we were successfully able to update machines but we found the following issue when running this script.

If a catalogue was deleted then recreated and the machine names were reused VSAN did not clean up existing VM folders causing the new machines to be created in folders with the a suffix _1 etc.

suffix 1 folders new machines

If the script is run where these duplicate folders exist it then errors.

vmware vsphere errors

With this failure, the VM loses its cache disk, only the OS disk and Identity disk are present.

mcs test update 1

If the Cache Disk is removed the machines will BSOD, when the IO is greater than the RAM.

This was resolved by confirming the removal of the machines and associated objects before deploying the catalogue.

Overall impression

The overall impression is good, and when comparing this to a more immature hypervisor it works well. VSAN performs extremely well, with a very good user experience. However, how something as fundamental as the MCS update failure we experienced on VSAN has slipped through the net is hugely disappointing!

If you found this article useful please give it a share and leave a comment below. Alternatively, if there are some topics you would like us to cover, suggestions are welcome.

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