When upgrading virtual hardware, consider these points:
Modification of the virtual hardware version on the vCenter Server Appliance is not supported. Likewise you should not manually install any additional version of VMware Tools inside the guest OS of the vCenter Server Appliance.
Upgrading a Virtual Machine to the latest hardware version is the physical equivalent of swapping the drive out of one system and placing it into a new one. Its success will depend on the resiliency of the guest operating system in the face of hardware changes. VMware does not recommend upgrading virtual hardware version if you do not need the new features exposed by the new version.
Before you upgrade the virtual hardware version of a virtual machine, create a snapshot or backup of the virtual machine in case there are issues post upgrade.
To automate this process, consider using vCenter Update Manager for virtual machine upgrades.
When you upgrade virtual hardware, no downtime is required for vCenter Server or ESXi/ESX hosts. For virtual machines, the only significant downtime is the time to shut down and restart the guest operating systems.
Note: From ESXi 5.5 onward you can schedule hardware version upgrade for next guest OS restart.
NIC configuration may be lost when upgrading from ESXi 3.5 to a newer hardware version. To workaround this issue, ensure that latest version of VMware Tools is running in the virtual machine before commencing hardware version upgrade.
Note: Upgrading VMware Tools must be done before upgrading the virtual hardware except for the guests running Linux distributions or FreeBSD releases that have vendor supported open-vm-tools installed in the guest.
Pre-requisite before you upgrade the virtual hardware:
Create a backup or snapshot of the virtual machine.
Upgrade VMware Tools. On Microsoft Windows virtual machines, if you upgrade the virtual hardware before you upgrade VMware Tools, the virtual machine might lose its network settings.
Verify that the virtual machine is healthy and available, with no inaccessible virtual disks, CD-ROM or ISO images, etc.
Determine the version of the virtual hardware by selecting the virtual machine from the vSphere Client or vSphere Web Client and clicking the Summary tab. The VM Version label in the Compatibility field displays the virtual hardware version.
Upgrading virtual hardware on a single virtual machine
To upgrade the virtual hardware of a single virtual machine:
Log in to the vCenter Server.
Power off the virtual machine.
Click the Updates tab.
In the VM Hardware Compatibility panel, click Upgrade to Match Host.
Power on the virtual machine.
Note: If the virtual machine has a Microsoft Windows guest operating system, the operating system detects a new device, configures the device, and may prompt you to reboot the guest operating system. If any unknown devices are recognized, the operating system may prompt you to configure the device manually.
For Windows guest operating systems, reboot the guest operating system to make the changes take effect.
Upgrading virtual hardware on multiple virtual machines
You can upgrade virtual hardware on multiple virtual machines in a single operation using the following steps:
Login to vCenter Server
Navigate to Menu > Hosts and Clusters.
Select a host or a cluster from the inventory and click the Updates tab.
Select VM Hardware.
VM hardware version upgrade must be enabled on first use, Click Enable. <====== If you get a message stating VM Hardware version upgrade must be enabled
The virtual machines on the host or cluster are listed.
To update the VM Compatibility and current status, click Scan Now.
Select the virtual machines whose hardware version you want to upgrade and click Upgrade to Match Host.
The Upgrade VM Hardware to Match Host dialog box appears.
(Optional) Expand Scheduling Options to postpone the upgrade.
You can select an option for virtual machines that are powered on, powered off or suspended.
Note: By default, the upgrade follows immediately.
(Optional) To configure the use of snapshots, expand Rollback Options and change the default settings.
To enable or disable taking of snapshots of virtual machines before upgrading them, select or deselect the Take snapshot of VMs check box.
The option to take snapshots is selected by default.
Select a period for keeping the snapshots:
Keep the snapshots indefinitely. Keep the snapshots for a fixed period.
Enter a snapshot name and, optionally, a description for the snapshot.
Include the virtual machine memory in the snapshot by selecting the respective check box.
Click Upgrade to Match Host.
The selected virtual machines are upgraded and the status is displayed in the Recent Tasks pane.
Ensuring that your virtual machine is upgraded and functional post hardware version upgrade
To ensure that your virtual machine is upgraded to latest hardware version:
In the vSphere Client, navigate to a virtual machine container object, such as a virtual machine folder, host, cluster, and so on.
Click the Updates tab.
Select your task.
Option
Action
Check the VMware Tools status of the virtual machines in the container object.
The information about the VMware Tools status appears in the Tools Status column in the table that lists all virtual machines in the selected container object. If the container object is a data center or a vCenter Server instance, you must first specify the cluster that you want to see results for.
Check the VM Hardware compatibility status of the virtual machines in the container object.
The information about the VM Hardware Compatibility status appears in the Status column in the table that lists all virtual machines in the selected container object. For each virtual machine in the object, you can also see the VM hardware compatibility and the host compatibility. If the container object is a data center or a vCenter Server instance, you must first specify the cluster that you want to see results for.
To ensure that your virtual machine is functional post upgrade:
Migrate the virtual machine from a host with an earlier ESXi/ESX version to a host with the latest ESXi/ESX version. For more information, see the Migrating Virtual Machines section in the vCenter Server and Host Management Guide.
Note: Upgrading VMware Tools must be done before upgrading the virtual hardware. Upgrading VMware Tools is not required for Linux O.S that have tools status as Guest Managed as they have vendor managed open-vm-tools installed in the OS.
Power on the virtual machine.
Note: In some instances, the operating system may require you to reboot the virtual machine after powering it on.
Ensure all the virtual machine network settings (such as IP, DHCP, and DNS) are correct.
Notes:
If you are using dynamic DNS, some Windows versions require to run the ipconfig /registerdns command.
If you are using DHCP, a new IP address may be assigned because the MAC address changes on the virtual NIC during the hardware upgrade. If you are using statically assigned DHCP addresses, ensure that you assign the new MAC IP address that you were using before the virtual hardware upgrade.