pg_test_fsync - Man Page

• Run the default fsync benchmark (5 seconds): pg_test_fsync
• Specify a custom test duration: pg_test_fsync [-s|--secs-per-test] seconds
• Use a specific filename (it must be in same filesystem that the pg_wal directory is or will be placed in): pg_test_fsync [-f|--filename] path/to/file

tldr.sh

pg_test_fsync [option...]

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​.

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​.

The environment variable PG_COLOR specifies whether to use color in diagnostic messages​. Possible values are always, auto and never​.

postgres(1)