On Saturday, March 29, 2025, Robert Treat <
rob@xzilla.net> wrote:
On Thu, Mar 27, 2025 at 5:57 PM David G. Johnston
<david.g.johnston@gmail.com> wrote:
> On Thu, Mar 27, 2025 at 2:28 PM Robert Treat <rob@xzilla.net> wrote:
>> On Thu, Mar 27, 2025 at 12:06 PM David G. Johnston
>> <david.g.johnston@gmail.com> wrote:
>> > I expanded upon the material regarding using different file systems and disks.
>> >
>> > I would like to add a similar "why" to the mount point recommendation but don't know what that would be. Suggestions welcomed.
>> >
>>
>
> If I mount the filesystem on disk2 to: /mnt/disk2
> Why do I need to create "/mnt/disk2/wal_files/" and point there instead of: "/mnt/disk2/"?
>
eventually came across this from
https://www.postgresql.org/docs/devel/creating-cluster.html#CREATING-CLUSTER-MOUNT-POINTS
"Best practice is to create a directory within the mount-point
directory that is owned by the PostgreSQL user, and then create the
data directory within that. This avoids permissions problems,..."
Which I do remember having tried to do it directly and the OS
complaining that my mount point wasn't owned by root and/or Postgres
complaining that the xlog dir wasn't owned by Postgres, so I think
this advice probably still holds.
Thank you, I can definitely work that in and it makes sense.
On the topic of verbosity, I found the wording for —pgdata in pg_basebackup to support the more complete description.
I believe that at least documenting external side-effects should be required. I’m less convinced that pre-conditions that will be checked by the application need to be listed. But for now I’m going to copy pg_basebackup as my example and at some point might get to doing a survey and proposing a new standard wording for —waldir and —pgdata descriptions regarding creation.
The comment regarding absolute paths will remain unwritten.
David J.
