The hardware version of a virtual machine reflects the virtual machine's supported virtual hardware features. These features correspond to the physical hardware available on the ESXi host on which you create the virtual machine. Virtual hardware features include BIOS and EFI, available virtual PCI slots, maximum number of CPUs, maximum memory configuration, and other characteristics typical to hardware.

When you create a virtual machine, you can accept the default hardware version, which corresponds to the host on which you create the virtual machine, or an earlier version. You can use an earlier hardware version in the following situations:
  • To standardize testing and deployment in your virtual environment.
  • If you do not need the capabilities of the newer version.
  • To maintain compatibility with older hosts.

Virtual machines with hardware versions earlier than version 11 can run on ESXi 6.0 hosts, but do not have all the capabilities available in hardware version 11. For example, you cannot use 128 virtual processors or 4080GB of memory in virtual machines with hardware versions earlier than version 11.

The vSphere Web Client and the vSphere Client allows you to upgrade virtual machines only to the latest hardware version. If virtual machines do not have to stay compatible with older ESX/ESXi hosts, you can upgrade them on ESXi 6.0 hosts. In this case, they are upgraded to version 11.
  • To maintain virtual machine compatibility with ESX/ESXi 3.5 hosts, upgrade the virtual machine on an ESX/ESXi 3.5 host, which results in a virtual machine upgrade to version 4.
  • To maintain virtual machine compatibility with ESX/ESXi 4.x hosts, upgrade the virtual machine on an ESX/ESXi 4.x host, which results in a virtual machine upgrade to version 7.
  • To maintain virtual machine compatibility with ESXi 5.0 hosts, upgrade the virtual machine on an ESX/ESXi 5.0 host, which results in a virtual machine upgrade to version 8.
  • To maintain virtual machine compatibility with ESXi 5.1 hosts, upgrade the virtual machine on an ESX/ESXi 5.1 host, which results in a virtual machine upgrade to version 9.
  • To maintain virtual machine compatibility with ESXi 5.5 hosts, upgrade the virtual machine on an ESX/ESXi 5.5 host, which results in a virtual machine upgrade to version 10.

A virtual machine can have an earlier hardware version than that of the host on which it runs in the following cases:

  • You migrate a virtual machine created on an ESX/ESXi 4.x or earlier host to an ESXi 5.0 host.
  • You create a virtual machine on an ESXi 5.0 host by using an existing virtual disk that was created on an ESX/ESXi 4.x or earlier host.
  • You add a virtual disk created on an ESX/ESXi 4.x or earlier host to a virtual machine created on an ESXi 5.0 host.

You can create, edit, and run different virtual machine versions on a host if the host supports that version. Sometimes, virtual machine actions on a host are limited or the virtual machine has no access to the host.

Table 1. ESXi Hosts and Compatible Virtual Machine Hardware Versions
Version 11 Version 10 Version 9 Version 8 Version 7 Version 4 Compatible with vCenter Server Version
ESXi 6.0 Create, edit, run Create, edit, run Create, edit, run Create, edit, run Create, edit, run Create, edit, run vCenter Server 6.0
ESXi 5.5 Not supported Create, edit, run Create, edit, run Create, edit, run Create, edit, run Create, edit, run vCenter Server 5.5 and later
ESXi 5.1 Not supported Not supported Create, edit, run Create, edit, run Create, edit, run Create, edit, run vCenter Server 5.1 and later
ESXi 5.0 Not supported Not supported Not supported Create, edit, run Create, edit, run Create, edit, run vCenter Server 5.0 and later
ESX/ESXi 4.x Not supported Not supported Not supported Not supported Create, edit, run Create, edit, run vCenter Server 4.x and later
ESX/ESXi 3.x Not supported Not supported Not supported Not supported Not supported Create, edit, run vCenter Server 3.5 and later

Virtual machine hardware versions earlier than hardware version 4 are not supported on ESXi 6.0 hosts. To make full use of these virtual machines, upgrade the virtual hardware.

Note: Virtual machine hardware versions 9, 10 and 11 features are limited to hardware version 8 and earlier when connected to the ESXi host or vCenter Server system using the vSphere Client.