PG_TEST_FSYNC(1)

✨ PG_TEST_FSYNC(1) — the pg_test_fsync(1) glow-up from the PostgreSQL 14.24 docs ✨

Okay bestie, welcome to the PG_TEST_FSYNC(1) page from the PostgreSQL 14.24 documentation — aka the manual for pg_test_fsync(1). It’s giving “let’s benchmark some WAL sync methods together” energy, and honestly? Iconic.

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🌸 NAME 🌸

pg_test_fsync — determine fastest wal_sync_method for PostgreSQL. That’s the whole assignment, no cap.

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💫 SYNOPSIS 💫

pg_test_fsync [option...]

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🦋 DESCRIPTION 🦋

Okay so pg_test_fsync is intended to give you a reasonable idea of what the fastest wal_sync_method is on your specific system, as well as supplying diagnostic information in the event of an identified I/O problem. So like, it’s both a speed check and a little detective. 🕵️‍♀️

🚨 Real-talk caveat, bestie: the differences shown by pg_test_fsync might not make any significant difference in real database throughput, especially since many database servers are not speed-limited by their write-ahead logs. So don’t treat this like a magic wand, fr fr.

pg_test_fsync reports average file sync operation time in microseconds for each wal_sync_method, which can also be used to inform efforts to optimize the value of commit_delay. Numbers with ✨purpose✨? We love to see it.

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💅 OPTIONS 💅

pg_test_fsync accepts the following command-line options:

• -f, --filename — Specifies the file name to write test data in. This file should be in the same file system that the pg_wal directory is or will be placed in. (pg_wal contains the WAL files.) The default is pg_test_fsync.out in the current directory. Put it where the WAL energy lives, iykyk.
• -s, --secs-per-test — Specifies the number of seconds for each test. The more time per test, the greater the test’s accuracy, but the longer it takes to run. The default is 5 seconds, which allows the program to complete in under 2 minutes. More time = more accuracy, but also more waiting; choose your fighter. ⏳
• -V, --version — Print the pg_test_fsync version and exit. Short and sweet.
• -?, --help — Show help about pg_test_fsync command line arguments, and exit. Your little map, bestie. 🗺️

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🌈 ENVIRONMENT 🌈

The environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never. Color-coded diagnostics? We love to see it. 🎨

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🔥 SEE ALSO 🔥

postgres(1) — go say hi.

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That’s the whole page, bestie. Cute sign-off: this one is from the PostgreSQL 14.24 documentation, dated 2026, and its manual tag is PG_TEST_FSYNC(1) 💖