Is there a way to tell which VMs won't migrate before going into maintenance mode? I need to put 12 servers in maintenance mode and would need to schedule an outage if a VM won't migrate. Thanks, Andy
It depends on the resource available in the cluster. For example you have 3 esx(i) host where each esx(i) can have 20 VM.. Now in a cluster totally you have 60 VMs. if you have only 40 VM's and you want to put 1 host in maintenance mode then this will work fine all the vm will migrate with no issue.
If you have 50 VM you can migrated 10 Vms of that host to another in cluster and put anohter 10 VMs in shutdown, then carry out the maintenance activity. IF yo have 60 VMs in cluster it means full loaded and you cant migrated vms to another in that cluster or you have to bring a new host in .
Here are few clarification you have enough resources and still maintenace mode doesnt migrate VMs of that host. reason is as simple as that HA enabled cluster with admission control and you put host with VMs in maintenace mode wont work refer below blog for some basic idea of it.
The message in blog is applicable for vsphere 4.x and lesser than that..
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My question was more on being able to tell that all guests will migrate off without actually going into maintenance mode. I know I have the resources in my clusters but some of my VM's won't migrate due to SCSI host bus sharring.
I have to test if a server will go into maintenance mode prior to doing the mantenance to a blade chassis so that I'll know I don't have to take an outage to one of the vm's and this is somewhat lengthy when they're 14 ESX hosts in one chassis.
If some of the VMs unable to move to other host due to some issues, then the host will not enter into maintenace mode.
You need to bring it the VMs if manual migration also doesn't work. So there shouldn't be any fear about VMs downtime while entering the host in the maintenace mode.