I was very unsurprised to see that this history starts a bit late. In 1992 I was working on HACMP/6000, which was a high-availability clustering product for IBM's AIX (though I worked at a company that was on contract to them). Databases were a primary use case, relying on shared storage instead of replication. We were hardly the first into that space BTW. DEC in particular had developed a lot of the concepts (e.g. locking models) that we and others at the time emulated, and the history in this space goes back even further than them. Were those systems as scalable as what we have now, or even as robust? Nowhere even close. But the erasure of that history still irks me. Modern distributed databases (and distributed systems in general) in their turn relied heavily on experience and concepts from those earlier systems, but rarely acknowledge the fact.