Today I had my 1st "Phone Advisory" with a large customer wanting some guidance on upgrading to Service Pack 2 for Exchange 2010. It was an excellent discussion, and even though SP2 has been out for about 6 months now, there are still many organizations of all sizes that haven't installed it yet. If you haven't performed this upgrade yet, here are a few things to help you through it.
First I'd recommend reviewing this TechNet article, it covers most of what you need to know.
One of the biggest things about this upgrade, is that it includes a schema update. Setup will automatically attempt to run the schema update, as long as the account your running it under is a member of both the "Schema Admins" and "Enterprise Admins" groups. In many larger organizations, it may not be possible for you as an Exchange Admin to perform the schema update. Luckily the schema update can be performed separately, however it must be done first or the Service Pack will not install. If you are unable to perform the schema update yourself, run it through your organization's change management process, and assist whoever has the rights to perform it. More information on how to run schema updates for Exchange can be found here. If you need to know exactly what is changed in the schema, consult the Exchange Server Active Directory Schema Changes Reference.
Once your schema update is complete, there are some prerequisites on the Operating System that need to be met before you can install the Exchange Service Pack, including either OS Service Packs, hotfixes, or both. For more information on the prerequsistes, check out this TechNet article. For Service Pack 2, there are some new prerequisites that apply only to servers with the CAS role installed. The SP2 Release notes contain a couple PowerShell commands that you can copy and paste to make installation of these new prerequisites easy.
The customer I worked with today had all 5 of the Exchange roles running on their own dedicated servers, which makes the upgrade process pretty straightforward, as outlined in the TechNet article I referenced earlier. You start with your Client Access Servers. If a hardware load balancing solution is being used, this process can be done without interrupting service to your end users. After your all your CASs have been upgraded, move on to your Hub Transport, then your Unified Messaging (if you have them), and finally your Mailbox servers. If your Mailbox servers are part of a DAG, there are some additional considerations, these are outlined in the aforementioned article as well.
If you have Multi-Role servers, you'll want to take a look at this Blog post from the Exchange Team on how to patch them.
So what are some "Gotchas?" when installing SP2?
When you run Setup, don't forget to run it with administrator level permissions (right click Run-As Administrator).
If you have the Unified Messaging Role (I've found this to be rather uncommon), AND you've installed additional language packs, you need to uninstall the language pack son your UM server(s) prior to installing the Service Pack. After the Service Pack has been installed, you can install the SP2 versions of any language packs that are needed.
If you have any Group Policies that define PowerShell Execution policies, it is important to make sure that the MachinePolicy and UserPolicy are set to "undefined". If they are not, the install may fail. To check your Execution Policy, run the command: Get-ExecutionPolicy -list For more information see KB2668686.
The version of the Management tools must match the version of Exchange installed on the server you want to manage. If you have the EMC installed on a Windows Vista or Windows 7 worksation, don't forget to update them, if you don't, they won't be able to connect to your servers until you do.
One important question I was asked today, was "is there a way to roll this update back?", and the answer is NO! Once the schema changes have been made, you can't undo them. Once a Service Pack has been installed on an Exchange server, you can't uninstall the service pack. Attempting to uninstall the service pack will result in Exchange being removed from the server.
If you haven't installed a Service Pack on Exchange 2010 before, I hope this article will help you in your endeavor, best of luck!