This is a great question!  I am also in the midst of trying to find a solid backup solution for Sage 300 CRE.  At the current time, our Sage server is a VM and I've got a nightly backup of the entire VM going to a local NAS, I am assuming that this method is sufficient, but I'd love to be able to know that I've got a good backup of just the DB in case we had to restore just data and not an entire VM.  I'm kind of surprised there isn't a built in backup script within Sage to automatically or manually kick off a DB backup in SQL with a specifiable backup output directory that takes into account users that haven't been logged out yet, or works around them (freezing the DB state momentarily like a VSS backup would or via some other mechanism).  

Thanks for the response, Andrew. Our Sage server is also on a Hyper-V VM and we also do nightly backups using Veeam. However, Sage specifically warns against differential/incremental backups, which Veeam does (nightly full backups would be way too big), and also says that the Sage data files cannot be in use to ensure the success of the backups. This is the crux of the issue as users are not closing out of Sage apps every night.

I am wondering if we should just have folks log into the server via RDP rather than using Sage directly on their workstations. We can then boot them out after a fixed amount of idle time. We do this for another client and it works very well.