Date: Fri, 14 Jun 2019 12:15:38 -0400
From: Stephen Frost <sfrost@snowman.net>
To: Bruce Momjian <bruce@momjian.us>
Cc: Fabio Pardi <f.pardi@portavita.eu>,
	pgsql-performance@lists.postgresql.org
Subject: Re: Fwd: upgrade to PG11 on secondary fails (no initdb was launched)
Message-ID: <20190614161538.GH2480@tamriel.snowman.net>
References: 
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 <68cf5e6c-8eb0-d8dc-08ec-78d8e910c17c@portavita.eu>
 <20190614033001.5jif725fxchtopg7@momjian.us>
 <b07e8a66-b122-8f41-03b3-6d2fc236f3e7@portavita.eu>
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Greetings,

* Bruce Momjian (bruce@momjian.us) wrote:
> On Fri, Jun 14, 2019 at 10:39:40AM -0400, Bruce Momjian wrote:
> > On Fri, Jun 14, 2019 at 03:12:29PM +0200, Fabio Pardi wrote:
> > > Using --size-only, tells rsync to only check the size of the blocks.
> > > That is: if the block is present on the destination, and is the same
> > > size as the origin, then skip.
> >=20
> > The files are _exactly_ the same on primary and standby, so we don't
> > need to check anything.  Frankly, it is really only doing hard linking
> > of the files.
>=20
> Here is the description from our docs:
>=20
>        What this does is to record the links created by pg_upgrade's
>        link mode that connect files in the old and new clusters on the
>        primary server.  It then finds matching files in the standby's old
>        cluster and creates links for them in the standby's new cluster.
>        Files that were not linked on the primary are copied from the
>        primary to the standby.  (They are usually small.)  This provides
>        rapid standby upgrades.  Unfortunately, rsync needlessly copies
>        files associated with temporary and unlogged tables because these
>        files don't normally exist on standby servers.
>=20
> The primary and standby have to be binary the same or WAL replay would
> not work on the standby.  (Yes, I sometimes forgot how this worked so I
> wrote it down in the docs.)  :-)

Right- this is *not* a general process for building a replica, this is
specifically *only* for when doing a pg_upgrade and *everything* is shut
down when it runs, and every step is checked to ensure that there are no
errors during the process.

Thanks!

Stephen

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