Spot checkpoint write pressure before it hurts
Requested checkpoints rising faster than timed checkpoints means WAL volume is ending checkpoint cycles early. Measure deltas around a representative workload before changing max_wal_size.
Problem
What you're actually looking at
The symptom as it shows up on a real server.
A write burst can reach max_wal_size before checkpoint_timeout. PostgreSQL still paces checkpoint writes, but the available window can end sooner, making I/O more intense. Measure timed/requested deltas instead of assuming every requested checkpoint is an unthrottled burst.
A batch job on Meridian's write path produces enough WAL to fill max_wal_size repeatedly. Users report periodic stalls that do not line up with any cron entry.
Simple terms
PostgreSQL spreads checkpoint writes to avoid flooding storage. A large WAL burst can force the next checkpoint cycle to start before the timeout, shortening the headroom available for that pacing. The timed-versus-requested counters tell you whether the clock or WAL volume is ending cycles; take before/after deltas around real work rather than reading lifetime totals.
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