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> Most distributed filesystems don't provide that guarantee though. It's a very nice guarantee, but it comes at a complexity cost, usually a performance cost (a
by pbowyer 6y ago
> Most distributed filesystems don't provide that guarantee though. It's a very nice guarantee, but it comes at a complexity cost, usually a performance cost (although there are clever ways to approach the perforance of a non-consistent system), and in particular it means the filesystems can't be used when the network connection is down.
Which distributed file systems do provide this guarantee? I can't think of one, so hopeful to learn something new today.
- 3np 6y agoI was curious as well and search turned up chubaofs - it claims to have "strong replication consistency" https://github.com/chubaofs/chubaofs https://github.com/chubaofs/chubaofs
- jlokier 6y agoHeh, 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.