OVH / are a bunch of muppets.
I have been dealing for 2 days with them in order to restore this server.
No luck.
Have RAID 1, have backup, but in practice nothing is working as expected.
I am moving all the websites to another host rather than dealing useless people.
Nothing is lost, all will be working normally without 24h, once the new server is properly configured.
Sorry about this unexpected shut down. sucks, their 99% uptime guarantee is a fucking lie.
After their "migration" many people got similar problems, here is a thread with other who are hangry too.

See you in 24h and thanks for your patience.