Vcenter upgrade - moving 4.1 host to 5.1 server

Hi all,

I have a 5.1 vcenter server that Im hoping to move my 3 ESX 4.1 hosts to. Im just wondering the best way to do this. I have currently migrated all VM machines to 2 hosts so that I have an empty host. for the next shoud I:

disconnect from existing vcenter server and connect to 5.1 server and Upgrade?

can I connect a 4.1 host to a 5.1 vcenter server?
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I'd upgrade this via VUM update manager, and yes the VCenter server is backward compatible, so you should be able to connect it to the 5.1 server.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Make sure you Disconnect the ESXi hosts from vCenter Server 4.1 first, before adding to vCenter 5.1.

vCenter 5.1 can manage ESXi 4.1 hosts.

Then use VUM.
MJB2011Author Commented:
OK thanks - I have installed the VUM update manager. So i can connect the host and upgrade that way.

When updating the host Im assuming the VM's (if any attached) will need to be shut down or migrated off?

also, will the VM's need to be updated to? if so can this be down whilst the VM is still running?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
The Host must be in maintenance mode, so VMs either off, or moved to another host.

VMware Tools, can be installed and upgraded, and if you so desire, you can Upgrade the Virtual Machine Hardware, BUT it's recommended, but VMs will still function without upgrade. (backup VMs first!)
Correct needs to be in maintenance mode so migrate all live vm's off, and yes you can upgrade the vm hardware version as well.
We just went through this.  We firstly upgraded our vCenter server from 4.1 to 5.1. Then I downloaded the ISO file and burned a CD.  While it is possible to do an upgrade with the UM, some people that we partner with for help with our Vmware environment suggested doing it from a CD. So I did one machine at a time, moved all VMs off the machine and put it in maintenance mode. Then rebooted from the CD and the a force migrate retaining all settings. When it was done it came up with the new ESXi version.. Only "issue" that I had was that I had set the NICs to 1000 Full and now they were all set to auto.  While this didn't keep them from working, I reset them to 1000 Full before putting VM's on them.  We did have an issue with one host and it turned out to be that a UEFI upgrade was needed to the hardware. After we did  that everything worked OK.  The only thing left after doing all of them was to upgrade the tools and the virtual hardware.

I'd check to make sure that your hardware meets the vmWare compatibility matrix and that you firmware is upgraded. We did all the firmware - although obviously missed the one - for the hosts and disk subsystems.

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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
New Installations, are often better, than Upgrades!

CPU requirements have changed alot from 4.1 to 5.1

Check the VMware HCL (Hardware Compatability Lists) here
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