Virtual Machine Monitoring For APD & PDL

As I use vCenter 6 more and more, I realize all the amazing new features.

One of the features, I came across was Virtual Machine Responses.
This feature allows you to specify what to do in the event of an APD and PDL. Come on, how cool is this?!?
I bet everyone ran into an APD or PDL situation before and asked him/her-self, why does VMware not offer a feature to restart the VM in such an event?

Virtual Machine Response 01

By default, when vSphere HA enabled, Virtual Machine Monitoring is disabled and so are the responses. However, you do not need to enable Virtual Machine Monitoring for Virtual Machine Responses to work.
The screenshot below show you the available settings for APD vs PDL. As you can see, in the event of an APD, you have 4 options:

  1. Disabled – do nothing and let the machine die
  2. Issue events – Issue a custom event
  3. Power off and restart VMs (conservative), will try to properly shut down the VM and restart it on another host
  4. Power off and restart VMs (aggressive), will forcefully shut down the VM and restart it on another host.


Similar settings are available in the event of PDL.



Important, this feature will NOT protect your VM from losing a RDM and will also not work with vSphere Fault Tolerance (FT)


vSphere 6 Fault Tolerance

VMware vSphere Fault Tolerance (FT) provides continuous availability for applications on virtual machines.

FT creates a live clone instance of a virtual machine that is always up-to-date with the primary virtual machine. In the event of a host/hardware failure, vSphere Fault Tolerance will automatically trigger a failover, ensuring zero downtime and data loss. VMware vSphere Fault Tolerance utilized heartbeats between the primary virtual machine and the live clone to ensure availability. In case of a failover, a new live clone will be created to deliver continuous protection for the VM.

The VMware vSphere Fault Tolerance FAQ can be found here.

Screen Shot 2014-12-30 at 5.58.55 PM


On a first glance, VMware vSphere Fault Tolerance seems like a great addition to vSphere HA Clusters to ensure continuous availability within your VMware vSphere environment.

However, in VMware vCenter Server 4.x and 5.x only one virtual CPU per protected virtual machine is supported. If your VM uses more than one virtual CPU, you will not be able to enable VMware vSphere Fault Tolerance on this machine. Obviously, this is an enormous short-come and explains why many companies are not using VMware’s FT capability.

So what’s new with vSphere 6 in regards to Fault Tolerance?

  • Up to 4 virtual CPUs per virtual machine
  • Up to 64 GB RAM per virtual machine
  • HA, DRS, DPM, SRM and VDS are supported
  • Protection for high performance multi-vCPU VMs
  • Faster check-pointing to keep primary and secondary VM in sync
  • VMs with FT enabled, can now be backed up with vStorage APIs for Data Protection (VADP)

With the new features in vSphere 6, Fault Tolerance will surely get much more traction, since you can finally enable FT on VMs with up to 4 vCPUs.