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From: Greg Sabino Mullane <[email protected]>
To: Nick Cleaton <[email protected]>
Cc: PostgreSQL General <[email protected]>
Subject: Re: Backups with filesystem snapshots
Date: Mon, 11 Aug 2025 12:41:12 -0400
Message-ID: <CAKAnmmLnSxW6ER0AXn9GxfL=84RWcei_7q2bPwieNyM+SS6mTQ@mail.gmail.com> (raw)
In-Reply-To: <CAFgz3ksJNVprBWLX4x=MdfJrG+uZSgUHTYGF35T=dJryJjz8zw@mail.gmail.com>
References: <CAFgz3ksJNVprBWLX4x=MdfJrG+uZSgUHTYGF35T=dJryJjz8zw@mail.gmail.com>

On Mon, Aug 11, 2025 at 9:01 AM Nick Cleaton <[email protected]> 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. :)

Cheers,
Greg

--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support


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