Upgrading ESXi 4.1 to ESXi 5.5 with Zero VM Downtime

[bernz]

Hi guys

I had recently upgraded to vCenter Server 5.5 U2 and I would like to upgrade my remaining PROD cluster with ESXi 4.1.

What is the recommended approach in upgrading it to ESXi 5.5 with ZERO virtual machine downtime?

Virtual machines will be retained in this cluster.

All vswitch & datastore must remain unchange. I have also newly setup VUM on the environment that is not part of this old cluster.

Appreciate you feedback.

[CoolRam]

If  your machine is running in the shared lun then you can use the cluster upgrade method . in which you will create the upgrade baseline using the VUM and start upgrade your host one by one . once the upgrade start before that it will migrate all the VM to another host.

So this way you upgrade all your host without VM down time .