The AndrewFileSystem:
Some of its authors noticed that AFS worked quite well for a while when you unplugged the network, due to caching, but has issues when writes occur. A research project called Coda was launched to allow fully disconnected operation: a laptop with a WLAN connection wandering in and out of range will seamlessly synchronize all files (and notify the user of conflicts). The project was quite a success.
Then its team decided that they could do better, so they sat down and started working on Intermezzo. This project is based on the same principles as Coda, along with the idea that it should be as fast as using a local filesystem, and should do everything over well established protocols (such as HTTP). I doesn't seem to be anywhere near production quality yet, though. Coda is unmaintained and pretty much unused nowadays.
AFS however continues to thrive, offering gigantic scaling capacities.
See also:
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