VMware's flagship products ESX 3.5 and Virtual Center 2.5 have been available for a little over a month now. When the upgrades were made available, there was much excitement on the newly touted features. So, many IT professionals quickly hurried off and downloaded their product updates and then came to a collective stopping point. How do we upgrade ESX while in use? Sure we upgraded from ESX 3.01 to 3.02 with very little impact. But the change from 3.0x to 3.5 may seem worthy of more preparation because the scope of the change is larger with some of the new features, like Storage VMotion. With the release, here is a simple upgrade strategy that many are adapting:
- Allocate two ESX 3.0x systems as 3.5 candidates (not everyone will be able to do this, I realise).
- Carve these two systems into their own cluster or data centre.
- Make sure all existing VMware DRS rules would be okay with two systems removed.
- Upgrade or fresh install one of the systems to ESX 3.5.
- Test migration from ESX 3.0x to the new ESX 3.5 system.
- Test VMware tools versioning and test any upgrade virtual machine tasks.
This strategy will replicate what you will likely face in a real upgrade situation, as you may not be able to. Because you may only be able to have a limited number of systems available for maintenance at any given time, it is good to be able to replicate that in a test datacenter or cluster. In smaller implementations, this could be repeated with one host where the migration test would be from a live ESX host. Evaluation software may also be a consideration to make available the correct number of hosts to simulate the co-existence of ESX 3.0x and 3.5.
Keep it moving
Should your configuration allow seamless migration between your ESX 3.0x and 3.5 hosts - that should not be a crutch for undefined periods of mixed versions. A good practice would be to have all hosts on the same version of ESX within a cluster. Larger environments may have difficulty moving all systems to the new version, but strategise within your Virtual Center configuration to determine the best configuration for temporary mixed versioning. The goal should be to get all systems on the same version enterprise wide - but only after you are completely comfortable with 3.5 in your infrastructure.
The horse's mouth
VMware provides many quality resources online, I've saved some work for you and collected some of the highlighted pieces here for review in relation to ESX 3.5 upgrades:
These resources are a good strategy in being well informed for the what your plan for ESX 3.5 will entail. Simply installing without preparation is surely a recipe for mis-configuration or incorrectly applying your configurations as intended. And the test upgrade procedure to become familiar with a mixed environment will allow you to clear the way for an end-state configuration of a single version of ESX.