Fittl: Waiting for Postgres 18: Accelerating Disk Reads with Asynchronous I/O

Lukas Fittl writes in detail on the pganalyze blog about the asynchronous I/O capability coming with the PostgreSQL 18 release.

Asynchronous I/O delivers the most noticeable gains in cloud environments where storage is network-attached, such as Amazon EBS volumes. In these setups, individual disk reads often take multiple milliseconds, introducing substantial latency compared to local SSDs.

With traditional synchronous I/O, each of these reads blocks query execution until the data arrives, leading to idle CPU time and degraded throughput. By contrast, asynchronous I/O allows Postgres to issue multiple read requests in parallel and continue processing while waiting for results. This reduces query latency and enables much more efficient use of available I/O bandwidth and CPU cycles.