We have an existing cluster that has very old CPUs (Sandy Bridge) and does not have EVC set on the cluster currently, We are wanting to expand this cluster with brand new Cascade Lake hosts. Our vCenter is on a separate management cluster, and we are at 6.7.
I want to make sure I understand the steps that would be required to do this work, and when the VMs would need to be rebooted or not, and when vMotions would fail, or not.
1. Set the existing cluster to EVC "Sandy Bridge". At this point the VMs should not need a reboot as they will all have been started on a Sandy Bridge host, and the instruction set the VM is using should not be higher than Sandy Bridge.
2. The cluster is now at EVC level "Sandy Bridge" as well as all VMs in the cluster will be at Sandy Bridge. vMotions should continue to occur normally.
3. Introduce the new Cascade Lake hosts into the cluster. The new hosts will inherit the cluster EVC mode of Sandy Bridge. vMotions for all VMs will continue to occur normally, and VMs can vMotion to the new hosts as well as the old hosts.
4. We can vMotion all VMs to the new hosts (assuming we have capacity, which we will), slowly turning down the old Sandy Bridge CPU hosts.
5. Once all VMs are on the new hosts, and all the old hosts are removed from the cluster, we can increase the EVC level of the cluster to Skylake (can't do Cascade Lake yet, as 6.7 doesn't support it). This should not incur an outage as all the VMs will be at Sandy Bridge EVC still.
I believe all the above is correct. However, I am a bit confused about the next part.
Once the cluster EVC level is set to Skylake, whenever a VM reboots, it will take on the EVC level of Skylake. However, before any individual VMs reboots, is it still able to vMotion once the cluster (and therefore all the hosts) are at the Skylake level? Basically, can a VM with EVC level Sandy Bridge vMotion to a host with EVC level Skylake?
Hopefully that was all clear. Thanks for any help.