Heh, even Microsoft SMB provides some level of coherency guarantee combined with performance, using its read and write leases. NFSv4 has a similar concept. It

Heh, even Microsoft SMB provides some level of coherency guarantee combined with performance, using its read and write leases. NFSv4 has a similar concept. It's an old idea by now. I actually don't know of any distributed (multi-master, fully replicated) filesystems that are published with this property. I only know it's possible because I designed one that isn't published. The basic principle is similar to CPU MESI caching but with predicate-scopes suited to a filesystem rather than cache lines. (Predicate-scopes are similar to predicate-locks in databases). As you know, multi-core CPU systems remain fast despite sharing memory, incurring significant overhead only for the changes that need to be communicated between cores. Same applies on a network.