Jepsen is just doing a kill -9 on the java process. I posted a comment on the blog: https://aphyr.com/posts/323-call-me-maybe-elasticsearch-1-5-0#comment-2357

Jepsen is just doing a kill -9 on the java process. I posted a comment on the blog: https://aphyr.com/posts/323-call-me-maybe-elasticsearch-1-5-0#comment-2357 https://aphyr.com/posts/323-call-me-maybe-elasticsearch-1-5-... First I made sure that read() goes through the page cache. (It does as long as there's no O_DIRECT) Then I went and checked the write ahead log on ES. Turns out from my reading that ES is considering a write to be durable if it is put into a userspace buffer. https://github.com/elastic/elasticsearch/blob/master/src/main/java/org/elasticsearch/index/translog/fs/BufferingFsTranslogFile.java#L190 https://github.com/elastic/elasticsearch/blob/master/src/mai... Data is pushed to kernel space whenever the buffer gets full. Then it is fsync'd on the timer.