I have run into this issue a few times now. My vcenter is a virtual machine. Running on a vDS. My ESXi host fails in a odd way: for example the host does not fail but the nic’s stop passing traffic. My isolation response keeps the vm powered on and HA see’s that the host is still accessing storage so no fail over happens. How do I get it back? Well I can power it off and move it to another host but I cannot power it on… Why?
Because my vDS is setup with static ports. Which means when vcenter is not available each ESXi host cannot start new virtual machines because they cannot allocate ports on the vDS. For a long time I ran my vcenter on a standard switch to avoid this issue. Now Vmware has provided a new option. In order to use this option we need to understand vDS port group types:
- Static Binding – The default setting, when you power on a virtual machine it is assigned a port and guarenteed that port going forward. The only time it looses this connection is when a vm is removed from the port group. The main issue with static binds port groups is they have a set number of ports available at creation time. If you try to power on a vm without available ports it fails. This has been fixed in 5.0 with a auto grow feature. Static assignments are made by virtual center not the host. Virtual center then creates the port on the ESXi host.
- Dynamic Binding- This is now deprecated and should not be used.
- Ephemeral Binding – This is a type of port binding to vm that is created by the host (not virtual center as in Static) The assignment is released by the host when a virtual machine is powered off or deleted. There are almost unlimited number of ports available (limited by host maximum number of ports).
So why don’t we just make all our port groups Ephemeral?
- They don’t scale as well you are only allowed to have 256 total port groups with ephemeral.
- They consume a lot more resources on each host.
- Vmware does not want you to do it… as evident by the auto-expand static binding.
So when do I use ephemeral?
On my vcenter port group so I can move it and power on without having a virtual center powered on.
Solved that Catch 22 …