Saturday, March 14, 2009

Exchange 2007 - post service pack roll ups

In the olden days, when I had dark hair, you used to have to reapply post service pack rollups every time you made a change.

      Example:

      Install Exchange 2000.

      Install Service Pack 1.

      Install a roll up.

Downstream you add Outlook Web Access. To patch this you would then apply service pack 1 again and then reinstall the roll up.

Exchange 2007 is different and it feels like it flies in the face of logic. Here is how you would *think* things would work...

      Install Exchange 2007 hub transport role.

      Install Service Pack 1.

      Install latest rollup.

So now you want to add the client access server role. Those files will create and then populate the \Program Files\Microsoft\Exchange Server\ClientAccess folder. Surely you would need to reinstall service pack 1 and then the roll up after adding that role?

Well, that is no longer the case.

The MSI service knows about the MSI and all MSPs installed for a given product. It actually 'calculates' and combines the MSI and MSP to figure out what the install should look like. It then installs that onto the machine. It doesn't add the role from the RTM MSI and then install the MSP which also makes sense. It does a more direct approach of taking the MSI and MSP, combining them together, and then forcing the machine to look like what it sees needs to be on the machine.

Now, that is logical thinking and means that once you apply a service pack or other roll up onto a machine you are then covered during any changes to the application. However, you do then need to leave the MSI available on the machine otherwise the update will fail and at best you are leaving your machine unupdated (I just made that word up). At worst you could have a problem with the application.

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