First off - the SCOM installation process has a lot of prerequisites which must be done in advance (obviously!) - make sure you have followed the Microsoft deployment docs in their entirety before starting the SCOM install. The following documents a couple of issues which caused significant delays in completing the installation of SCOM 2007 R2 - I hope my loss can be your gain.
If you are using named instances in SQL Server 2008 SP1, you cannot use underscores in the instance name - this nugget of information was provided by Microsoft Product Support.
The problem is observed during the install of the Data Warehouse database component when setup reports the following:
"The setup wizard was interrupted before Operations Manager 2007 R2 could be installed"
Then you will see:
"The setup failed. Do you want to open the setup log file (search for "value 3" in the file for locating failure)"
In the setup log file you may see references to "invalid namespace".
You need to uninstall the named SQL instance with an underscore in the name, and install a new instance with no underscores. However, you could simply install a 2nd instance with no underscores in the name and retain the original instance, if being used for other databases. Depending on your MS license model you may be allowed to run any number of instances on the one license (but check with your MS sales rep).
Note1: If you use the default SQL instance you will not see these issues.
Note2: I have seen this issue with SQL Server 2008 SP1 Standard Edition but I do not know if the problem exists in other versions of SQL Server 2008.
If you are using domain accounts for the SCOM services, there is a limit on the length of the service account names. If your service account names are very long they cause the installation of SCOM 2007 R2 Reporting to fail. After I entered the Data Warehouse Write Action account details - setup reported that it was not able to validate the supplied credentials.
My original service account was 25 characters in length (I like descriptive names, ok?) - my amended service account was 14 characters in length and this worked fine.
This SCOM infrastructure configuration contained a single OpsMgr server (hosting all roles) and a single SQL Server 2008 SP1 Standard Edition database server (with a named instance) hosting the OperationsManager database, OperationsManagerDW database, and the SQL Server Reporting services components. This is for a small site with approximately 100 Windows servers.
