On Mon, Mar 17, 2025 at 3:44 AM Jakub Wartak <jakub.war...@enterprisedb.com> wrote: > > dunno, I've just asked if it isn't suspicious to anyone except me else > that e_io_c > m_io_c rather than e_io_c <= m_io_c. My understanding > was always that to tune max IO queue depth you would do this: > a. up to N backends (up to max_connections; usually much lower) * e_io_c > b. autovacuum_max_workers * m_io_c > c. just one (standby/recovering) * m_io_c > > The thing (for me) is: if we are allowing for much higher IOPS "a" > scenario, then why standby cannot use just the same (if not higher) > IOPS for prefetching in "c" scenario. After all, it is a much more > critical and sensitive thing (lag).
This sounds quite reasonable to me. Given I just changed the default effective_io_concurrency to 16, what value would you say is reasonable for maintenance_io_concurrency? I based the eic change off of experimentation -- seeing where the benefits flatlined for a certain class of query on a couple different kinds of machines with different IO latencies. I don't feel strongly that we need to be as rigorous for maintenance_io_concurrency, but I'm also not sure 160 seems reasonable (which would be the same ratio as before). - Melanie
