We use a Synology running their proprietary RAID thing, with a hot spare. It's connected to fiber as central backup hub for all machines through read-only BitTorrent Sync. It's also functions as our Git Server. Next to that we have two remote backup sites for the most recent terabytes, and all Mac's have Time Machines running at home...

And of course everyone has a Time Machine as a fallback at home for their production machines.