For the current project I’m working on (it’s not technically software development), we’re using NFS within a single subnet that every desktop is hooked up to. The server is physically at the office and does not have internet access. We have some confidential files (healthcare and legal records) stored on it.
Since everyone has the NFS share mounted locally on their machine, simply adding a single file makes it appear on every other machine, without much overhead.
Encrypted backups are stored on- and off-site.