In French but with pictures: https://lafibre.info/ovh-datacenter/ovh-et-la-protection-inc... - probably a different OVH data centre, but they clearly have sprinklers there. The argument they made against gas extinguishers is by the time they have to use it, the data is gone anyway, and it's only going to trigger in the affected areas. It's also far safer for the people working there.