---
name: "pg_test_fsync"
section: "1"
platform: "linux"
package: "postgresql"
version: "18.6-4"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/pg_test_fsync"
---

# pg\_test\_fsync(1)

determine fastest wal\_sync\_method for PostgreSQL

## NAME

pg\_test\_fsync - determine fastest *wal\_sync\_method* for PostgreSQL

## SYNOPSIS

**pg\_test\_fsync** \[*option*...\]

## DESCRIPTION

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. However, 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. 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.

## 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.

- **-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.

- **-V** **--version**

  Print the pg\_test\_fsync version and exit.

- **-?** **--help**

  Show help about pg\_test\_fsync command line arguments, and exit.

## ENVIRONMENT

The environment variable **PG\_COLOR** specifies whether to use color in diagnostic messages. Possible values are always, auto and never.

## SEE ALSO

[**postgres**(1)](/postgres/1.md)