Hi Jeremy, I feel a little bit confused, could you please share more about the following?
> Vacuum is the more concerning case here, as large vacuums would consistently > cause the 16x IOPS amplification on replicas. I did not find a 16x amplification diagram in your github link. Maybe I am missing something? > I also think that visibility map and FSM reads were the largest cause of > replica reads when prefetch was disabled In my understanding, these forks are quite small. VM is 1/4000 and most of them are constantly in memory, so not lots of IO required? For FSM, I dont think they are WAL logged and therefore they can not be recovery prefetched. Additionally, most EBS-like block storage services offer a high IOPS-to-throughput ratio(usually 1:16-32kb), aggressive prefetching may not incur significant waste. This extra throughput capacity would likely go underutilized, especially it is running heavy sequential scan prefetching. Thanks, Shihao
