DRS move machine to different host type without EVC

[Farhad_b]

hi,

today i saw a strange thing in vCenter. there is a cluster that contains G9 and G10 servers (different cpu family) and EVC is off and configured an affinity rule that keep some VMs on G9 servers but today i saw that one of VMs that must run on G9 servers migrate to one of G10 servers by DRS and after 5 minutes again DRS move that VM to one of G9 servers!!!! when i try to move another machine from g10 servers to g9 server i get error that i must enable EVC to do this. now my question is why this happening? (VM on higher cpu class migrate to lower class without powering off vm) 

vCenter version: 6.7

G9 Servers ESXi: 6 U3

G10 Servers ESXi: 6.7 U3

Thanks in advanced.

[a_p_]

It depends on which host the VM was powered on. CPU features are presented to a VM only on startup.

André

[sjesse]

evc works by stripping cpu flags from the os basically as well. So DRS can move it to older cpus with evc off, the issue is going back. In a cluster you should always have evc set to same setting for all hosts

[Farhad_b]

thanks for replies. still i can't understand it. i've done a test. i powered on a VM on a g10 server and then i added this vm to the vm group that is created for affinity rule for G9 servers. DRS only generate event log that affinity rule is violated but it couldn't migrate vm to g9 servers. If I did the opposite maybe DRS migrate vm?

[a_p_]

A simple example:

• The Gen9 host supports CPU features: A + B + C
• The Gen10 host supports CPU features: A + B + C + D

• A VM that you power on on the Gen9 host can be live migrated to the Gen10 host, because it supports all of the VM's features (A, B, and C).
• A VM that you power on on the Gen10 host can not be live migrated to the Gen9 host because it lacks CPU feature D.

This is where EVC comes into play. In this case you'd set EVC to a mode that masks out feature D, so that VMs only get features A, B, and C regardless on which host they are powered on.

André

[Farhad_b]

thank you André for your example. in this example:

• A VM that you power on on the Gen9 host can be live migrated to the Gen10 host, because it supports all of the VM's features (A, B, and C).

DRS can migrate VM on G10 to G9 server again?

and i have another question when i migrate VM from one of G10 servers to another G10 server i got an error that I've attached.

G10 cpu servers are the same family (intel-skylake).

Thanks in advanced

[sjesse]

This can happen in hosts that aren't at the same patch level as well, there is cpu microcode on the host that gets updated some times and features of esxi that are required as well like mentioned below

[Farhad_b]

there are two VMs on G10 server that i want to migrate them to another G10 server. I got this when i migrate one vm and another vm migrate without any error and problem. Current Server that VMs reside on is newer version of ESXi 6.7 is installed. but i don't know why i got error when i want to migrate only for one VM?

[a_p_]

Do these servers have the same CPU, and microcode?
Have the VMs been powered on on the same host?

André

[Farhad_b]

i think these two VMs not power on the same server. as i found out when i power on VM on a host, it inherit CPU Id from this server and this Id will be not change even when migrated to another host. VM CPU Id when changed that VM shutdown on a new server and powern again. is it true?

[Farhad_b]

👆👆can anyone help me and answer my question in pervious post. Thanks a lot.

[a_p_]

I'm not exactly sure what to answer. The different reasons for this have already been explained.

Best bet is to enable EVC to avoid such issues in the future.

André

[Farhad_b]

Thanks a lot dear André

[Farhad_b]

in another environment that there are USC blade and HP G8 and G7 blade servers, i want to migrate VMs to new purchased DL380 G10 servers. i've installed ESXi 7 U2d on new G10 servers and them to vCenter 7 but esxi installed on baled servers are 6.5 and 6.7 and they added to vcenter 6.7. i worried if i live migrate VMs from blade servers to G10 servers,  i get evc error in feature when i migrate VMs between G10 servers. is it better to power off vms and migrate them to G10 servers and then power on them? 

thank you.