effective_io_concurrency
No restart — settable per sessiontuned by pgconfiguratorcount (number of concurrent I/O requests)
How many concurrent disk I/Os PostgreSQL will issue for prefetching.
What pgconfigurator would set
32 GB · 8 vCPU · NVMe · OLTP
Computing…
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What it does
effective_io_concurrency hints how many I/O operations can be in flight at once, mainly so bitmap heap scans can prefetch pages. Storage that handles many parallel requests (SSD/NVMe, RAID) benefits from a higher value.
How to tune it
0 disables prefetch (sensible for a single spinning disk). For SSDs use a few hundred; NVMe can go higher still. It pairs with maintenance_io_concurrency, which governs prefetch for maintenance operations like VACUUM.