Rebuilding a server from someone's memory

An engineer builds a client's environment properly. The documentation is written if there is time, which there generally is not, and the knowledge stays with the person.

Realised at failure

The gap is invisible until something breaks and the person who built it is unavailable. Then the business is reverse-engineering its own work under time pressure, in front of a client.

Change history is what diagnoses faults

Most faults follow a change. Without a record of what altered and when, diagnosis starts from first principles every time, which is slow and looks incompetent from the client's side.

It is also a valuation question

A managed-services business whose knowledge lives in individuals is worth less than one whose knowledge lives in records, because the former cannot be handed over. That matters at sale and at every staff departure before it.