PG_TEST_FSYNC(1)

📦 version 13.23, in opensuse-leap 16.0

🦋 pg_test_fsync — bestie edition 🦋

okay so this is the pg_test_fsync(1) page from the PostgreSQL 13.23 docs, and it's genuinely one of those little tools that's lowkey more useful than it looks 💅

✨ NAME ✨

pg_test_fsync — the tool that figures out the fastest wal_sync_method for your PostgreSQL setup 🎀

🌸 SYNOPSIS 🌸

pg_test_fsync [option...]

💖 DESCRIPTION 💖

so pg_test_fsync is here to give you a reasonable idea of what the fastest wal_sync_method is on your specific system, and it also hands you diagnostic info in case you've got an identified I/O problem going on 🫶

but real talk — the differences it shows you might not make any significant difference in actual database throughput, especially since like, a lot of database servers are not speed-limited by their write-ahead logs. so don't spiral, okay? 😭

what it does report is the average file sync operation time in microseconds for each wal_sync_method ✨ and that number is also genuinely useful if you're trying to optimize the value of commit_delay. iykyk 👑

💅 OPTIONS 💅

pg_test_fsync accepts the following command-line options, bestie:

  • -f, --filename — specifies the file name to write test data in. this file should live in the same file system that the pg_wal directory is (or will be) placed in. (pg_wal is where the WAL files hang out, in case you were wondering 🧚) the default is pg_test_fsync.out in the current directory.
  • -s, --secs-per-test — specifies the number of seconds for each test. more time per test = greater accuracy, but also the longer it takes to run. the default is 5 seconds, which lets the program finish in under 2 minutes ⭐
  • -V, --version — print the pg_test_fsync version and exit. simple, iconic.
  • -?, --help — show help about pg_test_fsync command line arguments, and exit. your little safety net 🙈

🌈 ENVIRONMENT 🌈

the environment variable PG_COLOR specifies whether to use color in diagnostic messages 💜 the possible values are always, auto and never.

🔥 SEE ALSO 🔥

postgres(1) — go read that one next, bestie 🫶

ngl the whole point here is: measure first, don't just vibe-guess your wal_sync_method 💀

and that's the whole page, no cap 🎀 this one's from PostgreSQL 13.23, dated 2025 — mwah, go run it on your own hardware and slay ✨👑

📦 where this page comes from