5 years ago
With a decent software RAID controller, it's not too hard to persuade it that a networked remote device is just another disc onto which it should be mirroring writers.
However, the remote disc will inevitably take longer to complete those writes than the local one. So your local system becomes constrained by the speed of the link. You can queue writes locally and send them over the link as bandwidth allows, but then you don't have a current mirror any more.
These days I'd be inclined to use ZFS snapshots every (arbitrary interval), with incremental send.