As most of us, we all start with some form of documentation in our serverpark/datacenter. This could be a simple excel sheet, or an existing intranet/database.
The problem with integrating a new CMDB like I-doit is that most of our data is already present in some form.

In our case we have an intranet page with server positions, an billing system with client info and we use IPPlan for the network documentation. All these systems
rely on a MYSql databases.

The problem with a CMDB is that your information will be duplicated and will get inconsistent over time, if for example a server is in your intranet and in your CMDB.
It would not help to import the data once, because it changes over time.

The solution would be a sort of "Live datalink" with your existing databases that could be integrated in I-doit. For example:

Client information -> Billing system (the only database that has this information) -> I-doit contact assigned to a server (Live information from the billing database).

or

Server position -> Intranet (the only database that has this information) -> I-doit server position assigned to a server (Live information from the intranet database).

I hope my explanation is clear. Please let me know what you think about this.