Our storage provider for site files, images, and assets had an outage that led to a full outage of Harmony. Live sites and the administrative portal were both down. After tracking down the problem we disabled asset serving across all live sites, which let us bring live sites and the administrative portal back online.
Harmony was in this state of partial outage for another three hours while our storage provider resolved their issues. We were fully back up and running by 4:30 pm Eastern.