Building a "Distributed" FTP Server?

austad asks: "At my company, we run a fairly large Web site. It's distributed on multiple servers in three geographic locations. In each of these locations, we have several Real Video servers which all serve the same content for redundancy, and load balancing. We have a central FTP server in one geographic location that files get uploaded to, and then replicated out to the Real Video servers. The problem with this model is that there is a single point of failure. We would like to put an identical FTP server in each location, and when a producer wants to upload a file, they are randomly directed to an active FTP server (we use a distributed DNS system that will direct users to machines that are marked as "up"), and they upload the file." (Continued in body...)

"The problem is keeping the other two FTP servers current. How does each FTP server know who has the most current file tree? What if multiple producers are uploading simultaneously, and each has been directed to a different FTP server? Keep in mind that when replicating, we need to delete files on the Realservers that are no longer in the file tree on the FTP server. "