We are trying to provide a cloud backup service to our customers. We want their backups to sync with the server in our office.
We have a Linux Server with Ubuntu 14.04 and a LenovoEMC px4-300r (10tb total) mounted to the server.
The goal is to take our customer's large backup (estimated to be around 40gb or more each) and put it onto an external HDD, take it over to our office, throw it onto our LenovoEMC, and then sync it with a folder on the client side.
We need something that will be able to only update the files that have changed. We previously used Owncloud but on its initial sync, it would sync the entire large backup over the internet regardless if the files already existed on the server or not.
So Owncloud is not a viable solution for us.
[Server] <---> [Client]
We would essentially like to do something similar to how Google Drive or Drop Box works but to use our own servers for storage rather than a third party.
What sort of solution out there can we use?
We have both Windows and Mac OS X clients so there would need to be cross platform capabilities.