VMware HA

toronto2456
toronto2456 used Ask the Experts™
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Hi,

I am managing 6.5 HA \ DRS Clusters with 5 ESXi hosts.

I know that Auto Start for VM is not configurable for the ESXi hosts that are member of Clusters .

and I know that HA will re start the VMs on remaining hosts in case of Host failure.

What happens if All host goes down and ESX hosts coming back online.

What happens the VMs then, especailly vCenter server appliance .
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Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
All VMs will restart on the hosts, they were hosted on when the hosts went down.

As the appliance is also a VM, it will also be restarted.

e.g. a complete power outage, where the hosts are not on UPS.

ALL OFF.... when Power comes back on.... ALL ON and restarted!

and as you also have DRS (if set to Automatic), when vCenter Server Appliance finally powers up, and on, and starts communication with the Cluster, it will also "rebalance" the VMs across the Cluster.

Is your next question HOW?

BUT it MUST BE HOST FAILURE, e.g. uncontrolled shutdown....... not human powered down or shutdown....

Author

Commented:
Thanks Andrew,

But in our case, VMs didn't get started. I don't know why. So I am looking Auto Start feature too. I know that in Cluster environment, Auto Start is not configurable as HA takes responsibility.

But I connected to ESXi Hosts in the cluster and I can enable the Auto Start on them and my vCenter applicance is shows Startup enabled.

So what would happen in this case.  Is this good practice to do so ?.
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
Something wrong with your HA then! They (the VMs should start up....I would test and fix this, but enabling and causing more conflict with another function!)

How did they fail ?

Did you ever test HA ?

This is the VMware KB, but it says nothing now for 6.5.....

https://kb.vmware.com/s/article/850

but....

and there is lots of noise, it does not work...

https://communities.vmware.com/thread/547938

It's because HA and Auto-Start effectively conflict and clash!
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Author

Commented:
Thanks Andrew

I am not sure actually as I was there why HA did not start VMs

But what kind of conflict do you think It will occur. Currnelty I have enabled Auto Start on All hosts.

Suppose all 3 host foes down from an power outage, then the first once came back,

do you say that they are going to fight for who is going to start the VM , Host auto start or VMware HA feature.

What is the best practice for this ?
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
Do you have it ENABLED ?

because...

2018-09-27-20_52_32-vSphere-Web-Clie.png
this is what it states - so these settings MAY NOT WORK!!!!!

did you see this ? how did you enable it ?

Best Practice is to not enable it. (or was).

In the past VMware have stated you cannot enable it, it's disabled.

So.... if you really have to enable it - YOU NEED TO TEST IT, like TESTING HA WORKS!

Have a read of this... sound familiar

https://www.reddit.com/r/vmware/comments/6j10i0/question_on_automatic_startup_of_vms_in_a_ha/

Author

Commented:
Thanks

Author

Commented:
Sorry , one question though,,

out of these ESXI host, if only one of them comes back , HA still can start the VMs on that host ?
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
Yes! within limits, it cannot start the all unless you have Resources, and depending on how you have configured HA settings!

If you have three hosts A, host B and host C

and have a cluster with VMs which is 100% on A, 100% on B, 100% on C...

would you expect ALL your VMs to run on a single host ?

depends on your specification?

Author

Commented:
I see. Thanks Andrew.

So in normal circumstances, Even if one hosts come back online , assuming that it has enough resources and vCenter appliance is configured as HA enabled, then that Hosts should start vCenter appliance, even if Auto Start is disabled.

And this is why Auto Start is not configurable on Hosts in VMware HA cluster.

So , The reason why vCenter appliances did not get started when ESX Hosts start coming back online after power failure is not the HA - Auto Start configuration but something else, again HA should have started the VMS

is my understanding is right ?

Thanks
VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017
Commented:
So in normal circumstances, Even if one hosts come back online , assuming that it has enough resources and vCenter appliance is configured as HA enabled, then that Hosts should start vCenter appliance, even if Auto Start is disabled.

Correct. If Hosts were shutdown in an uncontrolled fashion.

And this is why Auto Start is not configurable on Hosts in VMware HA cluster.

Correct a CONFLICT.... This has always been the way, as designed by VMware.

If HA is configured correctly, HA (FDM Agent is configured and designed to restart VMs in the Cluster).

All vCenter does, is configure the HA (FDM Agent) on each host, and it's these Agents which restart the VMs, not vCenter Server, so as vCenter Server is also a VM it will also restart vCenter Server (VCSA).

If HA is not restarting your VMs, then I would re-visit and check and test HA is working!
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017
Commented:
Yes, based on your Admission Control settings.

But your host must have all the resources available to run all your VMs!

otherwise they will not start, or if they do start, performance is going to be poor!

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