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:
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?
