I'm not on the inside of cockroachDB's raft implementation, but typically you've got a single thread processing AppendEntries requests in a defined order, exact

I'm not on the inside of cockroachDB's raft implementation, but typically you've got a single thread processing AppendEntries requests in a defined order, exactly one at a time, to guarantee the same order of execution on every node. There might be some small savings from doing a couple of updates concurrently here and there but your overall flow should be single threaded. As far as the address space and big SSDs thing.. I'd be willing to gamble on linux supporting mmap up to the biggest devices on the market, one way or another. Heck, there's only 16 more bits after that 47 before every FS under VFS has to be rewritten, right?