Replication is more efficient than you think
Anne Benoît, Thomas Hérault, Valentin Le Fèvre, Yves Robert · 2019
This paper revisits replication coupled with checkpointing for fail-stop errors. Replication enables the application to survive many fail-stop errors, thereby allowing for longer checkpointing periods. Previously published works use replication with the no-restart strategy, which works as follows: (i) compute the application Mean Time To Interruption (MTTI) M as a function of the number of processor pairs and the individual processor Mean Time Between Failures (MTBF); (ii) use checkpointing period [EQUATION] à la Young/Daly, where C is the checkpoint duration; and (iii) never restart failed processors until the application crashes. We introduce the restart strategy where failed processors are restarted after each checkpoint. We compute the optimal checkpointing period [EQUATION] for this strategy, which is much larger than [EQUATION], thereby decreasing I/O pressure. We show through simulations that using [EQUATION] and the restart strategy, instead of [EQUATION] and the usual no-restart strategy, significantly decreases the overhead induced by replication.