This scenario is known as a cold migration upgrade. When you use cold migration to move virtual machines from one host to another host, additional downtime is required for the virtual machines.

This scenario assumes that the hosts do not have VMotion, VirtualCenter, or vCenter Server.

The requirements for a cold migration upgrade are as follows:

One or more machines meeting ESX 4.0/ESXi 4.0 requirements.

Empty host storage sufficient to hold a portion of your virtual machines. Ideally, the storage should be large enough to hold all of the migrated virtual machines. A larger capacity for virtual machines on this extra storage means fewer operations are required before all your virtual machines are migrated.

Before you begin this procedure, install the vSphere Client. You can install the vSphere Client on the same machine with your previous version of the VI Client. You must have the previous version of the VI Client to connect to previous versions of VirtualCenter and ESX/ESXi. For a detailed description of the procedure, see Upgrade to the vSphere Client.


Power off or suspend the virtual machines on the ESX 2.5.x or ESX 3.x/ESXi 3.5 host.


For suspended virtual machine migrations, both hosts must have identical processors.


Evacuate the virtual machines from the host by moving the virtual machines to other hosts.


Upgrade ESX 3.x/ESXi 3.5 to ESX 4.0, or perform a fresh installation of ESX 4.0. A fresh installation is required if your legacy hosts are ESX 2.5.x.


(Optional) Create a VMFS3 datastore.


Move the virtual machines to ESX 4.0 host.


Upgrade your virtual machines:


If they are not already powered on, power on the virtual machines and upgrade to the latest version of VMware Tools. This upgrade allows you to use the new features of ESX 4.0./ESXi 4.0.


Power off the virtual machines and upgrade to the latest version of virtual hardware to take advantage of the new virtual hardware. vSphere 4.0 supports some earlier virtual hardware versions. See Basic System Administration.

The virtual machine upgrade process is different for ESX 4.0/ESXi 4.0. In earlier versions, you upgraded the virtual hardware upgrade before you upgraded VMware Tools. For ESX 4.0/ESXi 4.0, you upgrade VMware Tools before you upgrade the virtual hardware.

You can use either the vSphere Client or vCenter Update Manager to upgrade virtual machines. In a clustered environment, VMware recommends that you use vCenter Update Manager . See the vCenter Update Manager Administration Guide. If you are using the vSphere Client to upgrade virtual machines, see Upgrading Virtual Machines.


Upgrade your product licenses:


Either your new license keys are sent to you in email, or you get them using the license portal.


Apply the new license keys to your assets using the vSphere Client (or vCenter Server if you have it).

You must perform these tasks for each ESX 2.5.x host and the virtual machines on the hosts.