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From: Ron Johnson <ronljohnsonjr@gmail.com>
Date: Tue, 30 Apr 2024 20:31:45 -0400
Message-ID: <CANzqJaBm7ytQj7JYea+fRhfH_Hu-8LpEuqeg79XSBHuP72W-KA@mail.gmail.com>
Subject: Re: Linked directory or explicit reference
To: "pgsql-general@lists.postgresql.org" <pgsql-general@lists.postgresql.org>
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On Tue, Apr 30, 2024 at 7:00=E2=80=AFPM Senor Cervesa <frio_cervesa@hotmail=
.com>
wrote:

> Hi All;
>
> When doing an initial install of PostgreSQL on RHEL 7 or 8 derived OS via
> rpm, what are pros, cons and recommendations of these 2 procedures for
> utilizing a second disk?
>
> Secondary SSD or RAID mounted at /disk2.
>
> Option #1
>
>    1. install the rpm which creates basic user and home
>    2. Create symlink /var/lib/pgsql/15/data --> /disk2/data
>    3. initdb with no special options
>
> Or Option #2
>
>    1. install the rpm which creates basic user and home
>    2. initdb with --pgdata=3D/disk2/data
>    Probably using included 'postgresql-12-setup' script
>
> I also link /var/lib/pgsql/data  --> ../15/data so automation can
> reference postgresql.conf without knowing version (legacy stuff).
>

In my experience,The PgBackRest restore feature does not like symlinks.


> The install is automated with a bash script which handles several options
> including whether there is a second disk for DB. Scripting the install wi=
th
> or without the second disk is straight forward but I'm concerned with
> either scenario causing unforeseen differences.
>
> I don't think there's a benefit to using tablespace here but I have no
> experience with it. The systemd service is configured with a dependency o=
n
> the disk mount so I don't think there are different risks for starting
> postgres with missing data directory.
>
> I've run postgres in both scenarios and not had any issues. I'm intereste=
d
> in comments from others on their experience using these or other options.
>
Is the mount point just "/disk2" when using "--pgdata=3D/disk2/data"?  I've
gotten "directory not empty" errors when the mount point is
"/Database/x.y/data".

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<div dir=3D"ltr"><div dir=3D"ltr">On Tue, Apr 30, 2024 at 7:00=E2=80=AFPM S=
enor Cervesa &lt;<a href=3D"mailto:frio_cervesa@hotmail.com">frio_cervesa@h=
otmail.com</a>&gt; wrote:<br></div><div class=3D"gmail_quote"><blockquote c=
lass=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px soli=
d rgb(204,204,204);padding-left:1ex"><u></u>

 =20
  <div>
    <p>Hi All;</p>
    <p>When doing an initial install of PostgreSQL on RHEL 7 or 8
      derived OS via rpm, what are pros, cons and recommendations of
      these 2 procedures for utilizing a second disk?</p>
    <p>Secondary SSD or RAID mounted at /disk2.</p>
    <p>Option #1<br>
    </p>
    <ol>
      <li>install the rpm which creates basic user and home</li>
      <li>Create symlink /var/lib/pgsql/15/data --&gt; /disk2/data</li>
      <li>initdb with no special options</li>
    </ol>
    <p>Or Option #2<br>
    </p>
    <ol>
      <li>install the rpm which creates basic user and home</li>
      <li>initdb with --pgdata=3D/disk2/data<br>
        Probably using included &#39;postgresql-12-setup&#39; script</li>
    </ol>
    <p>I also link /var/lib/pgsql/data=C2=A0 --&gt; ../15/data so automatio=
n
      can reference postgresql.conf without knowing version (legacy
      stuff).</p></div></blockquote><div><br></div><div>In my experience,Th=
e PgBackRest restore feature does not like symlinks.<br></div><div>=C2=A0</=
div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;bor=
der-left:1px solid rgb(204,204,204);padding-left:1ex"><div><p>The install i=
s automated with a bash script which handles several
      options including whether there is a second disk for DB. Scripting
      the install with or without the second disk is straight forward
      but I&#39;m concerned with either scenario causing unforeseen
      differences.<br></p>
    <p>I don&#39;t think there&#39;s a benefit to using tablespace here but=
 I
      have no experience with it. The systemd service is configured with
      a dependency on the disk mount so I don&#39;t think there are
      different risks for starting postgres with missing data directory.</p=
>
    <p>I&#39;ve run postgres in both scenarios and not had any issues. I=
9;m
      interested in comments from others on their experience using these
      or other options.</p></div></blockquote><div>Is the mount point just =
&quot;/disk2&quot; when using &quot;--pgdata=3D/disk2/data&quot;?=C2=A0 I&#=
39;ve gotten &quot;directory not empty&quot; errors when the mount point is=
 &quot;/Database/x.y/data&quot;.</div><div><br></div></div></div>

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