We believe we've identified the source which caused the unexpected outage, and had to reboot one of our servers. The server is currently going through routine checks. We'll update you once we know more.
Thumbnail server has experienced filesystem corruption and is currently running foreground filesystem checks.
Even if some of the files end up missing because of this it's not going to be an issue due to missing thumbnails being automatically regenerated by the system.
Unfortunately a filesystem check of 5TB of data on a 14TB partition is going to take a while to complete even on server grade hardware and as such we currently do not have estimates for when the site will be back online.