I have an ESXi 5.5 host called ESXi1 in a host DRS group called "ESXi1 Host group". No other ESXi hosts are in that group, but there are 4 other ESXi hosts in the cluster. I have a VM called "VM1" in a Virtual machine DRS group called "VM1 virtual machine group". No other VMs are in that DRS group.
VM1 -> "VM1 machine group"
ESXi1 -> "ESXi1 host group"
There is a mandatory DRS rule that says that VMs in "VM1 machine group" can only run on ESXi hosts in the "ESXi1 host group". What happens when I try to put host ESXi1 into maintenance mode? Will it be able to evacuate VM1 since there are no other hosts in the group that VM1 has to run in?
Yes. Answer is 100% correct. If configured VM-Host affinity/anti-affinity rule is MUST, it can not be violated. Even vSphere HA honors the VM-Host must rules. Even you can not manually migrate that VM1 to other Host. Maintenance mode also can not evaluate the host. Even if there is CPU/Memory imbalance, DRS will still obey this rule.
If you want this rule to be flexible, then you can configure the same as "soft/should" rule. In this case, rule will be violated whenever it is absolutely required(like MM, HA does not honor this rule, you can manually migrate that VM to other, DRS for the sake of balancing cpu/memory can violet this rule) But note that in the immediate next invocation of DRS, DRS will try its best to resolve the rule violation.
To know which rules can be honored by vSphere HA :is vSphere HA aware of DRS affinity rules? | vThinkBeyondVM
Let us know if you need any other clarity.
Since it is a must rule I'm pretty sure the host will not enter maintenance mode as the VM can't be moved to another host
OK - anyone 100% sure of this before I try it?
Yes that is the correct answer
Yes. Answer is 100% correct. If configured VM-Host affinity/anti-affinity rule is MUST, it can not be violated. Even vSphere HA honors the VM-Host must rules. Even you can not manually migrate that VM1 to other Host. Maintenance mode also can not evaluate the host. Even if there is CPU/Memory imbalance, DRS will still obey this rule.
If you want this rule to be flexible, then you can configure the same as "soft/should" rule. In this case, rule will be violated whenever it is absolutely required(like MM, HA does not honor this rule, you can manually migrate that VM to other, DRS for the sake of balancing cpu/memory can violet this rule) But note that in the immediate next invocation of DRS, DRS will try its best to resolve the rule violation.
To know which rules can be honored by vSphere HA :is vSphere HA aware of DRS affinity rules? | vThinkBeyondVM
Let us know if you need any other clarity.
