How to sync two disks - continually?

I have to HDD drives on two different servers that I need to sync regularly. Until now, I've been using rsync over sshfs, first from one to the other, then from the other to the first, but this method is proving unsatisfactory. When a file is removed from drive A, it is not copied to drive B, but then copied from drive B to drive A. So I can never remove anything unless I do it from both drives. The same goes for renaming - renaming a directory on one drive soon results in two directories with different names but the same contents. Ideally I need something that keeps track of changes on one drive and then duplicates these changes on the other. Any suggestions?