Whilst doing a new TFS 2008 dual tier install I was getting a failure with a TF220050 error when I entered the data tier DB instance name. The setup wizard just said ‘failed to connect to data tier’, but you can find the actual error number in the install logs to be found under C:Documents and Settings[setup user]Local SettingsTemp

This error seems to be just a generic low level ‘cannot connect to the DB’; in my case it was caused by one of two issues:

  • The SQL server I was pointing at was a SQL 2000 not SQL 2005 (I had been given the wrong server name) – the moral is always check the version yourself.
  • Also analysis services was not running on the SQL  2000 box.

So I am not sure which is the actual cause of the error message here, version or missing OLAP service In my case the fix was to just connection to the correct SQL 2005 instance.