This scenario is known as a migration upgrade that includes datastore migration. The migration upgrade is a managed transition rather than a strict upgrade. By using VMotion to move virtual machines directly from one datastore to another datastore, you minimize downtime of the virtual machines.

The following example provides a high-level overview of the upgrade process in an environment with ESX 2.5.x and VirtualCenter 1.4.x, using upgrade VMotion to migrate your running virtual machines to ESX 4.0. The hosts in your environment must be licensed for and able to use VMotion.

You can perform a migration upgrade without VMotion. The only difference is the amount of downtime for the virtual machines.

Upgrade VMotion (also known as VMotion with datastore relocation) is a special case in which you perform a one-way VMotion. In this scenario, you move virtual disks from a VMFS 2 volume to a VMFS 3 volume. Requirements include persistent-mode disks, a VMFS 2 volume that is visible to the ESX 4.0 host, and compatible host CPUs.


Upgrade VMotion is required if you have ESX 2.5.x hosts.

The disadvantage of a migration upgrade is that this plan requires additional resources. A migration upgrade calls for sufficient resources to run the production environment partly on older hosts and partly on upgraded hosts. Any required redundancies and safeguards must be available on both upgraded and non-upgraded infrastructure during the transition.

The requirements for upgrade VMotion 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 production 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, complete the following tasks:


Install vCenter Server 4.0. You cannot upgrade VirtualCenter 1.4.x to vCenter Server 4.0. You must perform a fresh installation.

For the supported operating systems, database types, and other prerequisites, see the Compatibility Matrixes and the Installation Guide on the VMware vSphere documentation Web site.


Install the vSphere Client 4.0.

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 the supported operating systems and other prerequisites, see the Compatibility Matrixes and the Installation Guide.


Install ESX 4.0/ESXi 4.0.


Create a VMFS3 datastore with a capacity that is greater than or equal to the VMFS2 datastore on the ESX 2.5.x host.


Add the ESX 4.0/ESXi 4.0 host to vCenter Server.


Remove the ESX 2.5.x host from VirtualCenter 1.4.x and add it to vCenter Server 4.0.

For upgrade VMotion to work, the ESX 2.5.x and ESX 4.0/ESXi 4.0 hosts must be managed by the same vCenter Server.


Expose the VMFS2 volume to the ESX 4.0/ESXi 4.0 host.

Upgrade VMotion requires that both the VMFS2 and VMFS3 volume are visible to the ESX 4.0 host. VMFS2 volumes are read-only on ESX 4.0/ESXi 4.0 hosts.


Select a powered on virtual machine and migrate it.

Upgrade VMotion copies the disk from VMFS2 to VMFS3. This process takes a varying amount of time, depending on the size of the disk and the IO load.

The hardware version of the virtual machines is automatically upgraded from version 3 to version 4.


Optionally, upgrade the virtual machines further.


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 (version 7) 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.