To be clear, “Durability and the Art of Consensus” is not a paper.
> tl;dr: nodes don't necessarily persist state to local disk
In the consensus literature, this is sometimes referred to as “diskless crash recovery”. For example, see work by Dan Ports.
> Local recovery actions, or any other kinds of node-specific details, have no relevance or influence on the information communicated thru the the global consensus protocol.
This goes directly against the central finding of PAR, which gives counter-examples where your statement does not universally hold true.
Again, it’s not intuitive. And that’s why it won FAST18—because it says “everything we know is wrong”. Complete red pill and mindbender.
More broadly, there's no concept of "crash recovery" at the system level, which has any meaningful utility. Nodes are either there or they're not there, exactly how they crash or recover from their crashes are irrelevant to the overall distributed system, insofar as if a crashed-and-recovered node comes back online, it's gonna need to re-sync with its peers before it can talk to anyone else, and that's not anything to do with "crash recovery" related to local disk or anything like that (which is all implementation details of the node itself) -- it's just normal node synchronization, orthogonal to any state storage stuff of the node.
PAR is something that your system can maybe implement, it's not any kind of rule or definition or requirement that all systems of some classification must satisfy..!