I'm outlining a plan to upgrade four ESX 3.5 U4 hosts to vSphere and I'd like some verification from the community that I'll be able to perform this upgrade with no downtime besides the VMware Tools Upgrades and the VMware Hardware Upgrades.

1) New install of vCenter

We want to change physical machines vCenter is running on. The databases aren't terribly important at the moment, so we're willing to have a fresh start on vCenter 4.0.

  • Create new Datacenter
  • Create new cluster

Questions: Do I need to add the current ESX 3.5 hosts to this cluster? Do I need to remove them from the existing cluster? Disable HA before doing that?

2) Host Upgrades

Do this for all 4 hosts:

  • Put 1 host in maintenance mode, then shut it down.
  • Fresh install of vSphere Re-add it to the same cluster

Questions: Can I run a vMotion from an ESX 3.5 host to an ESX 4 host? 3) VM Upgrades

For All VMs, done up to 4 days after the host upgrades (need a weekend for the downtime)

  • Upgrade VMware Tools
  • Power the machine down
  • Upgrade Virtual Machine Hardware
  • Power on the machine

Questions: Does this change the guest MAC address? Will we be OK running without the hardware upgraded for four days?


Answer 1. Yes and yes - simply break a host from the 2.5 cluster, remove it from the inventory and add it to a 4 VC datacentre (it doesn't need to be in a cluster at this point and I wouldn't cluster until all hosts are v4 myself).

Answer 2. Yes, back and forth in fact until you upgrade the machine version.

Answer 3. Yes and yes, MACs change with machine upgrade & reboot but you can manually retain them if you wish, and yes v4 machine VMs will run and run forever on v4 hosts, there's no NEED to upgrade them to v7 until you need the features it adds.

Good luck and come back with any more questions - by the way, you're on the right track - in-place upgrades of hosts and VC sucks ;)

  • 1
    Yep, vmware's upgrade processes don't really work, fortunately the architecture lets you re-build all the components at the upgraded version, without taking the entire environment down. Definitely the way to go. – Chris Thorpe Mar 3 '10 at 19:41
  • Re: #1- When you say "I wouldn't cluster until all hosts are v4 myself" you mean added to the vCenter 4.0 datacenter, not necessarily running ESX 4? – andyhky Mar 3 '10 at 20:06
  • no, I mean you only need a cluster for DRS and HA, vmotion works between unclustered hosts why not wait until all your hosts are upgraded before clustering. – Chopper3 Mar 3 '10 at 20:37
  • I did an in-place upgrade to VCenter just the other day -- 2.5 to 4.0. It went flawlessly. VCenter 4.0 can drive ESX/ESXi 3.5 hosts with no problems. – Joe Mar 4 '10 at 20:08
  • I know it can, and often does, go very well but there's so many stories of it corrupting databases, forcing wipe/rebuild's, odd inconsistent problems etc that most people - it they have the option - choose to build from scratch. – Chopper3 Mar 4 '10 at 20:27

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