Jamie Lokier wrote:
Look up "one-phase commit" or even "zero-phase commit". (The terminology is cheating a bit.) As I've understood it, all commit protocols have a step where each node guarantees it can commit if asked and node failure at that point does not invalidate the guarantee if the node recovers (if it can't maintain the guarantee, the node doesn't recover in a technical sense and a higher level protocol may reintegrate the node). One/zero-phase commit extends that to guaranteeing a certain amounts and types of data can be written before it knows what the data is, so write messages within that window are sufficient for global commits. Guarantees can be acquired asynchronously in advance of need, and can have time and other limits. These guarantees are no different in principle from the 1-bit guarantee offered by the "can you commit" phase of other commit protocols, so they aren't as weak as they seem.
For several common Paxos usages, you can obtain consensus guarantees well in advance of actually needing that guarantee, making the entire process quite a bit more async and parallel.
Sort of a "write ahead" for consensus. Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
