vCenter Server upgrade from 5.1.1 to 5.5.0

Current version:

vCenter server:       5.1.0 Build 1063329
ESXi hosts:           5.1.0 Build 1117900


New version:

5.5.0b

ESXi software file:  VMware-VMvisor-Installer-5.5.0-1331820.x86_64-Dell_Customized_A01   (we have Dell servers so using the latest Dell provided 5.5 installer)
VCenter server:      VMware-VIMSetup-all-5.5.0-1476387-20131201 (5.5.0b)




There are a lot of blogs and post and documentation on upgrading so i am not going to bore you with screenshots and detailed explanation but just give me short point summary of how my upgrade process:

PRE-CHECKLIST:
Firstly I would recommend reading the VMware best practices kb as well as the installation/upgrade guide for VMware:
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2052329

1. As always, first off start with BACKUPS:
• Create snapshot/backup of vCenter Server virtual machine. 
• If available I recommend a third party backup/snapshot of vCenter for instance I made use of Commvault to a take a snapshot and store.  If vCenter upgrade fails it is not easy to revert/recover the snapshots since cannot start vCenter server.
• Create SSO backup by selecting the following on server where SSO is installed  "Programs -> VMware -> Generate vCenter Single Sign-On backup bundle"
• Open command prompt and change directory to where you have specified your SSO installation directory, default "C:\Program Files\VMware\Infrastructure\SSOServer\script
• Run "cscript sso-backup.wsf /z"  (files storage on desktop)
• http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2034928
• Create backups of databases for VCenter Server (VCDB), SSO (VCSSO) and Update Manager (VCUPDATE).
2. Check COMPATIBILITY for vCenter plug-ins on new versions:
• Verify that all third party plugins are compatible with the new version of VMware.
3. SSO - seems to be a lot of users having issues with SSO upgrade with a few pitfalls.
1. Warning 250000: Verify that your certificate for SSO is not expired, if so renew before upgrade. http://www.boche.net/blog/index.php/2013/11/12/single-sign-on-warning-25000/  (Very well written article on this warning and how to work through it)   I am still making use of my firstly created self-signed certificates and everything went fine.
2. The registry key I had to change from IP to FQDN in order to install otherwise you get a notification during the installation. Look at my other blog with images of upgrade to see this error message.  KB 2060511 - Change registry for SSO "HKEY_LOCAL_MACHINE\Software\VMware, Inc.\VMware Infrastructure\SSOServer\FQDNIP" to be FQDN and not an IP address.  http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=206051

INSTALLATION

Copy vCenter server install ISO to server and attached with virtual iso application for instance "Daemon tools".  I do this because if server is rebooted then you have the ISO attached through vCenter server client or web client it will loose the connection.

Simple or custom component install?
My two cents:  I am not a big fan on the simple install because I don't know what is exactly happening during the upgrade process and if a problem appears it is difficult to figure out which component failed, whereas with custom install you know which component you are installing.  Also if you have components installed on multiple servers you have to use the custom install.

We are going to perform below steps for vCenter Server upgrade - (the visual and text guidance in installer has been much improved by VMware)
1. Upgrade vCenter Single Sign-On
2. Upgrade vSphere Web Client
3. Upgrade vCenter Inventory Service
4. Upgrade vCenter Server
5. Upgrade vCenter Update manager
5. Upgrade vSphere client
6. Upgrade vCenter compatible plug-ins
7. Upgrade Distributed Switches

Upgrade problems experienced:
All of the upgrades went very smoothly without much interaction or problems except for the following -

Error:  Update manager vCenter health status failed.
Fix:      Change the service account for "VMware vSphere Update Manager Service" to same account as used for vCenter server service.

Error:   Storage monitoring service - initialization failed error on health status
Fix:      Change the service account for "VMware vSphere Profile-Driven Storage Service" to same account as used for vCenter server service. Restart service

UPGRADE ESXi: (error "Cannot run upgrade script on host")

There are multiple methods to upgrade each ESXi host to new release which can be read here -
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2058352
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2032756

We make use of vSphere Update manage to upgrade ESXi hosts, so can only start on this once vCenter and update manager has been upgrade to 5.5:
Firstly import the new iso to ESXi images. (does not work while still on 5.1)
Give the iso a baseline name
Create new Baseline group called for instance "ESX host 5.5 upgrade"
Select "host upgrade" for host baseline.

I did run into errors with upgrading the ESXi host from 5.1 to 5.5 which is addressed and fixed in the follow up blog post.