pg_test_fsync

Description

pg_test_fsync is intended to give you a reasonable idea of what the fastest [wal_sync_method (enum)

   wal_sync_method configuration parameter](braised:ref/runtime-config-wal#wal-sync-method-enum-wal-sync-method-configuration-parameter) 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 (integer)
  
   commit_delay configuration parameter](braised:ref/runtime-config-wal#commit-delay-integer-commit-delay-configuration-parameter).

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.