Migrating a cluster to new hw, use of EVC.

[JohanWest]

Hi guys,

I´m about to migrate a production cluster to new hosts/new hw.

The existing cluster is running about 30 vm´s within 3 HP DL380G5 (Intel X5460).

The hosts are ESXi 4.0.0 U1 build 208167.

vCenter is 4.0.0 Build 208111.

The newcluster will be running on 4 HP DL360G7 (intel X5650), and they are using the same ESXi version as above.

Is it possible to migrate the vm´s without any downtime? And what is the best way to do this?

It´s not possible to do vmotion from an "old" host to a new host because of the difference between the CPU´s (the newhosts is atm outside the old cluster).

So I guess I have to enable EVC in the "old" cluster, put the new hosts in it and do vmotion of the vm´s to the new hosts (EVC mode: Intel Xeon 45nm Core2 seems to be working).

And when all vm´s have been moved to the new hosts, I´ll remove the old hosts from the cluster, but now I want to enjoy the full potential of the new CPU´s.

Can Idisable EVC in the cluster now? How will this affect the vm´s? Do they need to be restarted to “see” the new CPU?

Or is there a better way to do this migration? I really don´t want to have downtime.. But if that’s the only way.. Well, that’s life I guess..

Best regards Johan

[WessexFan]

Hi Johan,

Currently you have 3 hosts running only 30 vms and you are going to have 4 servers running 30vms? This is too much hardware for your environment but a good problem to have. This is good if you want to scale-out in the future. I'm sure that you do.

Your CPUs will not have any issues. You are moving from G5 to G7 and both of the cpus are supported, so your migration should be seamless if you add your new hosts to the existing cluster and vmotion all of the vms over. All of your hosts will need to be in the same cluster in order for vmotion to be successful and EVC must be enabled.

As far as turning off evc after the migration, it is up to the administrator. If all of the cpus are of the generation, then I don't see any issues with not enabling evc. EVC simply opens up cpu 'restrictions' so vmotion can occur between cpus of different generations of the same manufacture (Intel, AMD)

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1005764

You raise a good question: I would tend to think that the vms would need to be restarted, but the hypervisor on the new hosts may automatically tell the vms of the new processor and enable functionality "on the fly". I dont have a good answer for this..my apologies.

[JohanWest]

Thanks for your answer Wessex,

I have another cluster as well, but running on older hw (IBM x3850 with Intel 7130N proc.) and about 30-40 vm´s more.

These vm´s will be migrated to the new hw too, but Idon´t think its possible to do that "live". EVC wont help me here I´m affraid.

And as you said, with this new environment we can scale-out in the future.

One question remains, say that I have added my new hosts to the cluster, enabled EVC to be able to vmotion vm´s to the new hosts and after that, removed the old hosts from the cluster.

What I have now is a EVC cluster, but no "old" hosts in it. Im still forcing the CPU´s to a "lower"point of there capablilities (right?)

So whats recommended here? I guess I have to disable EVC in order to take full advantage of the new CPUs. But is a vm reboot require?

Whats the pros and cons?

Johan

[WessexFan]

Hi Johan!

No, you are not forcing your new cpus to a lower point of capability. EVC is just enabled to make cpus of different generations "play nice" with each other if you need to vmotion vms between those hosts. If you have hosts on the same generation, then EVC may be turned off. In the future, however, if you add more hosts with say G9 (made that up), then the cluster will have to have evc re-enabled.

Your vms will not have to be rebooted when enabling/disabling EVC.

Good luck!