Identify upgrade requirements for ESXi hosts

Host needs at least 2 cores, Host needs 64 bit CPU, host needs to support lahf and sahf CPU instructions, 2 GB RAM, 1 or more gigabit ethernet or better NICs,

Recommendations – Be sure you have enough RAM, Dedicated NICS for each function, Keep VM disks isolated from ESXi host, be sure to always use client when provisioning storage, larger cache and faster processors improve performance and be sure all HW is on the HCL.

Identify steps required to upgrade a vSphere implementation

  1. Upgrade vCenter Server
    • This can be upgraded so long as the previous version is 4.1 and is not running on Windows XP.  XP is no longer supported
    • Can also be a new build if preferred.
  2. Upgrade VMware Update Manager
    • Provides ease of upgrading and patching the hosts.
  3. Upgrade or re-install all ESX(i) hosts.
    • Can be done without downtime.  vMotion is supported across vSphere 5 and vSphere 4.x hosts so bring them down in maintenance mode one by one.
    • Reapply host licenses at the end of this step.
  4. Upgrade VMware tools in all VMs
    • Will require a reboot of Windows based VMs
  5. Upgrade VMFS Volumes
    • This can be done while VMs are running.
    • 4.x hosts will not be able to read new VMFS5 volumes, but 5.x hosts will be able to read VMFS3 volumes.
  6. Upgrade VMs Virtual Hardware
    • VM must be powered off to perform this function.
    • 5.x can run VMs with v7 and v4 hardware.

There are many different upgrade scenarios listed in the vSphere Upgrade Guide and I would suggest going through them all.

Upgrade a vNetwork Distributed Switch


Select vDS and click ‘Upgrade’ on the summary tab.  Follow the wizard.

See vSphere Networking Guide.

Upgrade from VMFS3 to VMFS5


  • VMFS2 volumes cannot be directly upgraded to VMFS5.  They must be upgraded to VMFS3 and then upgraded to VMFS5.
  • All hosts accessing the VMFS5 volume must be at ESXi 5.x or later.
  • Volume being upgraded needs to have at least 2MB of free blocks available as well as one free file descriptor.


  • Select host from inventory, Configuration->Storage.
  • Select the datastore and click ‘Upgrade to VMFS5’
  • After completed, must perform a rescan on all hosts associated with the upgraded datastore.

Differences from VMFS3

  • Support for greater than 2TB storage devices.
  • Standard block size is 1MB and still supports 2TB virtual disks
  • Support for greater than 2TB disk size for RDM in physical compatibility mode.
  • Ability to reclaim storage space on thin provisioned arrays.
  • Inplace upgrade that doesn’t affect running VMs
  • Smaller subblock sizes (was 64K, now 8K)
  • GPT partitioning instead of MBR

You do not need to have a 1MB block size to upgrade.  Any new VMFS5 datastores are created with a 1MB block size, but if upgraded, it will maintain the existing block size of the datastore.

Upgrade VMware Tools

Same upgrade process as 4.x.  Can be done through the VI Client or though VUM.  To note, vSphere 4.x hosts can run 5.x VMs and vSphere 5.x hosts can run 4.x VMs.

Upgrade Virtual Machine hardware

Process is the same as it was with version 7 upgrade.  VM must be powered off.  If you would like to reach some of the new config maximums then you will need to be at hardware version 8.

Upgrade an ESXi Host using vCenter Update Manager

Straight forward.  Can use VUM to do an orchestrated upgrade of all the hosts in your inventory by using  an upgrade baseline or a baseline group.  See page 92 of the Upgrade Guide for more information and the process.

Determine whether an in-place upgrade is appropriate in a given upgrade scenario

Upgrade paths which are not supported include

  • ESX/ESXi 3.x hosts: You must upgrade them to ESX (see next point) or ESXi version 4.x.
  • ESX 4.x host that was upgraded from ESX 3.x with a partition layout incompatible with ESXi 5.0.
  • You cannot use Auto Deploy to upgrade or migrate version 4.x ESX and ESXi hosts to ESXi 5.0, because version 4.x ESX and ESXi hosts are deployed by the traditional method of installing the software on the host hard disk.
  • You cannot change the installation location of the hypervisor (for example to move from local disk to a flash card.