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
========
