No, they did not. Plan 9 was designed long before any high availability/CAP theorem/distributed databases lessons were learned: it embodies the Unix mindset of

No, they did not. Plan 9 was designed long before any high availability/CAP theorem/distributed databases lessons were learned: it embodies the Unix mindset of reliably available nodes talking over tcp. Failover/distributed consensus/orchestration/load balancing/network split tolerance/replication could be built on top of 9P servers, but all of these concepts are pretty alien to Plan 9 itself.