My first proper software development job was to consolidate the 7 different CMDBs that the company had - they were an ISP/hosting provider who had done a rapid succession of acquisitions, all of which came with their own database of hardware.
Some of the data was so bad that we ended up having one guy who's job was to physically audit what hardware was really in the data centres, and then attempt to reconcile that with the CMDB data.
Some of the data was so bad that we ended up having one guy who's job was to physically audit what hardware was really in the data centres, and then attempt to reconcile that with the CMDB data.