Overdriving server fans.
 

Hopefully a fan expert out there can shed some light on this as so far I've not found any info googling. What happens if the flow rate thorugh a server is greater than the fan spec? For example; You have a server located in a contained cold aisle with a maximum fan flow rate of 400 cfm. However it just so happens that the airflow coming into the contained area is double this. So now you have 800 cfm needing to go through the server. The air flow has little option but to overdrive the fans (assuming a perfect seal around the containment). What is likely to happen to the server/fans? Will the bearings wear out? Or will the fans/fan motors easily cope with being driven by the airflow? Or will something else happen entirely?

Thanks in advance,
J