Re: ESX 4.1 to ESXi 5.1 migration or upgrade

Hi,

    Please go through the below mentioned articles/docs

http://pubs.vmware.com/vsphere-51/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-51-upgrade-guide.pdf

http://kb.vmware.com/kb/2021202

http://kb.vmware.com/kb/2032756

Reply to your questions "my plan is install a ESXi5.1  Virtual center.

Move the vms from one of the esx 4.1  to other host in the same cluster and disconenct this ESX 4.1 server and install with ESXi5.1 and conenct to the new virtual center server and share the LUNs and unregister the vms from esx 4.1 VC  and register them in ESXi5.1  VC and power ON"

1.Set-up VC >

                   vCenter Server 5.1 requires vCenter Single Sign-On and Inventory Service. You  must install these components in this order:

1. vCenter Single Sign-On
2. Inventory Service
3. vCenter Server

Once you are done with the VC setup,you can go ahead and connect your existing ESX/ESXI host.Move forward with the upgrade on the respective host one by one if you cant afford to have any downtime.

Note:Ensure you have a VC&DB backup prior to upgrade