Starting around October 28, 2012, Hurricane Sandy disrupts power in the New York City area for a few days, including the Chappaqua, New York, area where Clinton’s private email server is located. On October 30, an email exchange between Clinton’s deputy chief of staff Huma Abedin and another Clinton aide discusses that Clinton’s private server is down. Abedin’s main email account is hosted on the server.
Clinton’s computer technician Bryan Pagliano meets with staff from the department’s Information Resources Management (IRM) to find out if the department could provide support for Clinton’s server. Staffers tell Pagliano they can’t help because it is a private server.
This appears to be a very rare instance in which the existence of the server is mentioned to other department employees. (US Department of State, 5/25/2016)