On Wed, Jun 20, 2018 at 10:35 AM, Jerry Jelinek <jerry.jeli...@joyent.com> wrote:
> As Dave described in his original email on this topic, we'd like to avoid > recycling WAL files since that can cause performance issues when we have a > read-modify-write on a file that has dropped out of the cache. > > I have implemented a small change to allow WAL recycling to be disabled. > It is visible at: > https://cr.joyent.us/#/c/4263/ > > I'd appreciate getting any feedback on this. > > Thanks, > Jerry > > For reference, there's more context in this thread from several months ago: https://www.postgresql.org/message-id/flat/CACukRjO7DJvub8e2AijOayj8BfKK3XXBTwu3KKARiTr67M3E3w%40mail.gmail.com#cacukrjo7djvub8e2aijoayj8bfkk3xxbtwu3kkaritr67m3...@mail.gmail.com I'll repeat the relevant summary here: tl;dr: We've found that under many conditions, PostgreSQL's re-use of old > WAL files appears to significantly degrade query latency on ZFS. The > reason is > complicated and I have details below. Has it been considered to make this > behavior tunable, to cause PostgreSQL to always create new WAL files > instead of re-using old ones? Thanks, Dave
