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The procedure for upgrade to VMware vSphere 5.1 is quite similar to the upgrade path to vSphere 5.1 (and almost similar also to the upgrade path to vSphere 5.0) and is well described in the specific guide (vSphere Upgrade Guide).

And first to all, you have to analyze the pro and the cons of a product upgrade, for more information see also: VMware vSphere 5.5 – Upgrade or not upgrade? You have also to consider (particularly for small enviroment) if apply an upgrade or rebuild.

Anyway, some points are quite common for each major vSphere upgrade:

  • HCL: the Hardware Compatibility List must be checked before each upgrade (each vSphere major release as a specific HCL that could be different). Also the software part must be checked (on the VMware Product Interoperability Matrix) to verify the compatibility of some specific part (like for example the DBMS).
  • Firmware: this aspect is related to the previous point… each major release can require a minimum firmware level (especially for servers and storage)… usually a good approach could be update to latest stable firmware (but check with vendor recommendation).
  • Hosts: in can be upgrade (with an in-line process) to ESXi 5… but only in some cases (for example not when ESX was upgraded from version 3.x)… and is not possible change the destination of the installation (that goes in the boot partition). Usually a rebuild could be a better option.
  • Drivers and modules: some 3rd part modules or drivers can prevent an upgrade of ESXi /ESX. Check their compatibility with ESXi 5 and, if needed, remove them before the upgrade.
  • Plugin: the vCenter plugins must be verified before the upgrade of vCenter Server… considering also that the vSphere Web Client require new type of plugin designed for this interface.
  • View: you need to upgrade it to View 5.5 (Horizon View 5.3 is needed).
  • SRM: same as View. You need to upgrade it to SRM 5.5 before upgrade vSphere.

Knowm issues

There is a list of known issues, many are listed in the release notes and the most critical ones are also often listed directly on the download page. Obviously, if you the latest version available both the vCenter Server and ESXi you can reduce these problems.

This is a list of some possible problems:

  • The Trouble With SSL Certificates and Upgrading to VMware SSO 5.5
  • KB 2060511 (Upgrade from vSphere 5.1 to vSphere 5.5 rolls back after importing Lookup Service data)
  • KB 2061008 (vCenter Server 5.5 displays a yellow warning in the Summary tab of hosts and reports the error: Quick stats on hostname is not up-to-date)
  • KB 2035510 (Logging into vCenter Server 5.1 or 5.5 using the “Use Windows session credentials” option fails with the error: Cannot complete login due to an incorrect username or password)

Upgrade steps

The order of the different steps is almost the same:

  • Upgrade the backup software in order to have compatibility with vSphere 5.5 (and of course be sure to have a backup of your environment)
  • Upgrade the vCenter Server to version 5.5 with all its components (included the plugin)
  • Upgrade the ESXi hosts
  • Upgrade the VMware Tools (note that the upgrade to VMware Tools 5.5 require a Windows reboot)
  • Optional (and only if you really need it), upgrade the VM virtual hardware
  • If you came from vSphere 4.x, upgrade VMFS to version 5 (but consider also to requild your datastore)

For more information of the complete upgrade steps, when you have more VMware products, see the KB 2057795 (Update sequence for vSphere 5.5 and its compatible VMware products).

In the next posts there will be more information about the vCenter Server and ESXi hosts upgrade procedure.


Virtualization, Cloud and Storage Architect. Tech Field delegate. VMUG IT Co-Founder and board member. VMware VMTN Moderator and vExpert 2010-24. Dell TechCenter Rockstar 2014-15. Microsoft MVP 2014-16. Veeam Vanguard 2015-23. Nutanix NTC 2014-20. Several certifications including: VCDX-DCV, VCP-DCV/DT/Cloud, VCAP-DCA/DCD/CIA/CID/DTA/DTD, MCSA, MCSE, MCITP, CCA, NPP.