Date: Mon, 26 Feb 2024 14:24:25 -0500
From: Stephen Frost <sfrost@snowman.net>
To: norbert poellmann <np@ibu.de>
Cc: pgsql-admin@lists.postgresql.org
Subject: Re: Would you ever recommend Shared Disk Failover for HA?
Message-ID: <ZdzlafGnXC4fQAww@tamriel.snowman.net>
References: <20240222185937.M23609@ibu.de>
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Greetings,

* norbert poellmann (np@ibu.de) wrote:
> https://www.postgresql.org/docs/current/different-replication-solutions.html
> is listing a shared disk solution for HA.

Yeah.  Frankly, it's bad advice and we should remove it.  "Rapid
failover" is a bit laughable compared to replication when you consider
that crash recovery can take a very, very long time (depending on how
much outstanding WAL has been written since the last checkpoint but with
extended checkpoints and single-process WAL replay, crash recovery could
be on the order of hours ...) and promoting an online replica takes only
moments.

Ditto for block-based replication.

Probably should talk about WAL shipping more as "Physical Replication".

At the least, physical replication should really be listed first and
then logical replication, perhaps even in a distinct "included as part
of PostgreSQL" section with everything else pushed down to "some other
things exist that you could try"...

Thanks,

Stephen

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