Date: Tue, 12 Aug 2025 13:58:43 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Greg Sabino Mullane <htamfids@gmail.com>
Cc: Nick Cleaton <nick@cleaton.net>,
	PostgreSQL General <pgsql-general@lists.postgresql.org>
Subject: Re: Backups with filesystem snapshots
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On Mon, Aug 11, 2025 at 12:41:12PM -0400, Greg Sabino Mullane wrote:
> On Mon, Aug 11, 2025 at 9:01 AM Nick Cleaton <nick@cleaton.net> wrote:
> 
>     If I take an instantaneous filesystem-level snapshot of the postgres
>     data directory underneath a running postgres server, is that a safe
>     backup without doing any pg_start_backup/pg_stop_backup ?
> 
> 
> Safe, yes[*], but not particularly recommended except for special cases, like
> spinning up a fast QA cluster. For backups, use a Postgres-aware battle tested
> system like pgBackRest that offers more flexibility and more safeguards.
> 
> * Assuming your hardware/OS drivers are being honest with you about fsync
> 
> 
>     starting up from that snapshot should look the same as recovering from an
>     unclean postgres shutdown
>     due to a kernel panic.
> 
> 
> Yes, for all practical purposes it would be identical. Technically more similar
> to pulling the plug on the server. :)

Also, be careful that any tablespaces are also in the same snapshot.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Do not let urgent matters crowd out time for investment in the future.