Questions regarding vSphere "shared nothing" migration 5.5 -> 6.5

Hi,

In our data center we have two separate vSphere vCenter clusters (but they do share the same VM and VMkernel LANs). One is running vSphere Standard 5.5 and the other is running vSphere Enterprise Plus 6.5. Both have their own SAN. Each cluster can not "see" the other cluster's SAN.

The questions:

NOTE: We wish to accomplish the following without lowering the EVC mode on the new cluster. The new cluster IS running at a higher EVC mode than the old.

1) Is it possible to "disconnect" a host from the old 5.5 Standard cluster and "connect" it to the new 6.5 cluster, and then vMotion + Storage vMotion any VMs it may be managing over to a host + storage in the new 6.5 cluster - without any VM down time?

2) After performing the procedure in question 1), would it then be possible to "disconnect" that same host from the 6.5 cluster and "connect" it to the old 5.5 cluster once again?

3) Are there risks / consequences / other things we should be aware of? We do know that we should disable HA on the old cluster before attempting this.

Br,
Hans
LuftHansi-DKAsked:
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Luciano PatrãoICT Senior Infraestructure  Engineer  Commented:
Hi,

1 - Yes you can add a 5.5 host into a vCenter 6.5 and yes you then can move/migrate VMs between the hosts and datastores. But if hosts do not share the same Datastore this cannot be done with VMs power on. You need to power off VMs to do this.

How to remove/add ESXi hosts: https://kb.vmware.com/s/article/1004775

2 - Yes is possible.

3 - Since is not possible to do it life, the answer is in the 1.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
1) Is it possible to "disconnect" a host from the old 5.5 Standard cluster and "connect" it to the new 6.5 cluster, and then vMotion + Storage vMotion any VMs it may be managing over to a host + storage in the new 6.5 cluster - without any VM down time?

I would use remove, rather than disconnect, because this will remove the vCenter Server Agent!

Yes it is possible, you can disconnect from existing cluster and add to new cluster, BUT if you new Cluster has an EVC baseline you need to check it because the new EVC baseline will be applied to the existing host, and it will not apply to a host running VMs if the VMs are using those instruction sets which need to be masked by EVC!

2) After performing the procedure in question 1), would it then be possible to "disconnect" that same host from the 6.5 cluster and "connect" it to the old 5.5 cluster once again?

Yes. It would be best to REMOVE the host and not disconnect.

3) Are there risks / consequences / other things we should be aware of? We do know that we should disable HA on the old cluster before attempting this.

There will always be risks an issue, in doing this.
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LuftHansi-DKAuthor Commented:
Hi Andrew,

Thank you very much for your quick reply.

A couple of clarifying questions:

1a)
You are saying that "hot" vMotion + Storage vMotion is possible - without downtime - correct? And if so, it follows that the first answer in this tread (from "Luciano") was incorrect - do I understand this correctly?


1b)
Regarding "remove" vs "disconnect": In the following article from VMware, it states "Verify that all virtual machines on the host are powered off, or migrate the running virtual machines to a new host by using vMotion.":

https://docs.vmware.com/en/VMware-vSphere/5.5/com.vmware.vsphere.vcenterhost.doc/GUID-D3FC9B42-1075-4A28-9C3C-34BE67F385ED.html

So, if that is correct, then at the very least we will experience downtime at the point where we must shut down the VMs in order to remove the host - correct? Then we can go to the new cluster and "Add host..." that old host there - correct? Then start up the VMs and hot migrate them (vMotion + Storage vMotion) to any of the new hosts in the new cluster - yes? Then, finally, do the reverse to get the host back into the old cluster (again, I do not need to move VMs from the new to the old, this is only to get things back to "normal" in the old)...?


1c)
On our old cluster --> Manage --> Settings --> VMware EVC it says: VMware EVC is disabled
On our new cluster --> configure --> VMware EVC it says: VMware EVC is Disabled

So we do not, in any way, need to concern ourselves with EVC (as long as we use "remove" to get the host out of the old cluster) - Correct?


2a)
Same question as I wrote in 1b above...


3a) I hear ya!

Br,
Hans
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
1a. Shared Nothing Migration, so technically it's not a Storage vMotion, it's a Shared Nothing Migration,

"You can use vMotion to migrate virtual machines to a different host and datastore simultaneously. In addition, unlike Storage vMotion, which requires a single host to have access to both the source and destination datastore, you can migrate virtual machines across storage accessibility boundaries."

Source
https://pubs.vmware.com/vsphere-51/index.jsp#com.vmware.vsphere.vcenterhost.doc/GUID-561681D9-6511-44DF-B169-F20E6CA94944.html

1b.  VMware recommendation, like any changes to a production system, but  vCenter Server is just a management server, it does not affect running VMs, Remove is cleaner, because it removes the Agent!

1c. Very much depends on the processor generation in use. for a Live  Migration (vMotion). This is checked before a vMotion between different CPUs if there is a mismatch, vMotion will not continue and a warning will be shown.

If all your host processors are the same not an issue. If they are different, you may need to enable EVC. if you add the Host to a cluster.
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LuftHansi-DKAuthor Commented:
Thank you very much, Andrew.
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