# pgtestfsync

pg_test_fsync

pg_test_fsync

1

Application

pg_test_fsync

determine fastest

wal_sync_method

for

PostgreSQL

pg_test_fsync

option

# Description

pg_test_fsync is intended to give you a reasonable idea of what the fastest [???](#guc-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 [???](#guc-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