You are probably familiar with RAID-1, which is a mirroring technique for synchronizing data between two or more disks for the sake of redundancy. Normally, RAID-1 mirrors data between several local disks, but you can also sync them over Ethernet. This is not conventional RAID-1 but at least comparable.
Data safety is very important but often neglected. How important keeping one's data safe really is gets often recognized when disasters already happened. This article covers a few ideas how to prevent data loss even if your hard drive crashes or your house is on fire.