Re: Documentation for initdb option --waldir

On Wed, 2025-03-26 at 17:34 -0700, David G. Johnston wrote:
> +  <para>
> +   The <filename>pg_wal</filename> subdirectory will always exist within the
> +   data directory.  This is where <productname>PostgreSQL</productname>
> +   sends its write-ahead log (<acronym>WAL</acronym>) files.
> +   Specifying the <option>--waldir</option> option turns this subdirectory entry
> +   into a symbolic link. In general, this is only useful if the remote location
> +   is on a different physical device.  An existing directory must be empty and
> +   should not be a mount point.  The directory will be created
> +   (including missing parents) if necessary.
> +  </para>

I think that it is very valuable to have WAL on a different file system on the
same storage device.  The idea is that growing data files cannot exhaust the
space available for WAL.

How about this:

    There is always a <filename>pg_wal</filename> within the data directory.
    By default, it is a directory where <productname>PostgreSQL</productname>
    places its write-ahead log (<acronym>WAL</acronym>) segment files.  If
    you create the <acronym>WAL</acronym> location somewhere else using the option
    <option>--waldir</option>, <filename>pg_wal</filename> will be created as
    a symbolic link pointing to that <acronym>WAL</acronym> location.
    If the directory already exists, it must be empty and should not be a mount
    point.  The directory will be created (including missing parents) if necessary.

Yours,
Laurenz Albe