4 Replies Latest reply on Dec 4, 2019 10:04 AM by a.p.

    EVC mode steps

    jadedpuppy Novice

      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.

        • 1. Re: EVC mode steps
          scott28tt Champion
          User ModeratorsVMware EmployeesCommunity Warriors

          Moderator: Moved to vMotion & Resource Management

          • 2. Re: EVC mode steps
            a.p. Guru
            Community WarriorsUser ModeratorsvExpert

            First of all, "Yes" to your 5 statements. Well explained.

            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?

            An individual VM's EVC mode will only be changed after a full power-cycle (power-off, power-on), a simply reboot will noch change the VM's EVC mode.

            The CPU features are pinned to a VM at power-on. As long as it isn't power-cycled you can vMotion the VM from older CPUs to newer ones (provided that the new CPU exposes all the older CPU's features).

             

            André

            • 3. Re: EVC mode steps
              jadedpuppy Novice

              Andre, thanks for your confirmation of my understanding.

               

              I just want to make sure that I understand your answer.  Once the only hosts left in the cluster are the Cascade Lake hosts, running at Skylake EVC level, and all the VMs are still at Sandy Bridge EVC level.  Before those VMs (still at Sandy Bridge) are power-cycled, are they going to be able to be moved around by DRS as they normally would?  In other words could VM1, at Sandy Bridge EVC, currently sitting on host1 (Cascade Lake CPU, at Skylake EVC) by vMotioned to host2 (Cascade Lake CPU, at Skylake EVC) within the cluster?

               

              I believe you are saying this should work, which is my understanding as well, but I want to be very clear about my question.  Thanks again.

              • 4. Re: EVC mode steps
                a.p. Guru
                Community WarriorsvExpertUser Moderators

                Yes, that's how it works.

                It should even be possible to vMotion the VMs back to the old host until they are restarted with the higher EVC mode in place.

                 

                André