I was discussing something with one of my former colleagues a couple of days ago. He asked me what the impact was of running VMware View in an environment without HA.
To be honest I am not a View SME, but I do know a thing or two about HA/vSphere in general. So the first thing that I mentioned was that it wasn’t a good idea. Although VDI in general is all about density not running HA in these environments could lead to serious issues when a host fails.
Now, just imagine you have 80 Desktop VMs per host running and roughly 8 hosts in a DRS only cluster on NFS based storage. One of those hosts is isolated from the network…. what happens?
- User connection is dropped
- VMDK Lock times out
- User tries to reconnect
- Broker powers on the VM on a new host
Now that sounds great doesn’t it? Well yeah in a way it does, but what happens when the host is not isolated anymore?
Indeed, the VMs were still running. So basically you have a split brain scenario. The only way in the past to avoid this was to make sure you had HA enabled and had set HA to power off the VM.
But with vSphere 4 Update 2 a new mechanism has been introduced. I wanted to stress this, as some people have already made assumption that it is part of AAM/HA. It actually isn’t… The question for powering off the VM to recover from the split brain scenario is generated by “hostd” and answered by “vpxa”. In other words, with or without HA enabled ESX(i) will recover the split brain
Again, I am most definitely not a Desktop/View guy so I am wondering how the View experts out there look against disabling HA on your View Compute Cluster. (Note that on the Management Layer this should be enabled.)
Brandon says
I assume if you were using a pool based method, meaning users didn’t have a specific VM assigned in your environment, then no HA would be OK. The downed host would become disconnected and hopefully new machines would be available pretty soon on the others. Since those VMs aren’t specific it wouldn’t matter if it was a new machine. Actually, if you know you don’t have HA, then your design should have your pool big enough to handle the incoming onslaught of unexpected connections anyway. I don’t understand why you would do that, HA is included in almost every licensing model except the most basic.
David B says
Don’t forget, update 2 + pcoip needs an extra patch: http://kb.vmware.com/kb/1022830 !
mittim12 says
As Brandon stated a non persistent type of pool with a proper design should be able to function without HA. With folder redirection, roaming profiles, and the fact you are not dependent on a certain VDI machine you should be able to pick up on any other available machine.
I like having HA enabled but in a high density environment you could easily cause some storage issues if 150+ plus VDI machines start coming up across the cluster.
Barry says
i know this is an old forum but if anyone could answer this question for me that’d be great.
If you turn on HA using View 5.x, on a floating pool and a ESX host disconnects, wouldnt the VMs move over but come back in an Already used state?
dave says
Barry,
Agreed this is an old forum, but that has been our experience when a host has failed w/HA enabled. The machines become unavailable, HA restarts them on another host, when they come back up the desktop agents check in with the connection broker then go to an “Already Used” state and have to be manually cleaned up in View.