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From: Laurenz Albe <[email protected]>
To: Greg Sabino Mullane <[email protected]>
To: Colin 't Hart <[email protected]>
Cc: PostgreSQL General <[email protected]>
Subject: Re: wal segment size
Date: Wed, 17 Dec 2025 18:58:45 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAKAnmm+yoNEQCV3qXceXm9rNoOAPYK0DQCpSqLkNGvGuOQ3W=A@mail.gmail.com>
References: <CAMon-aQ8X7H7jCC6ggKm9Uzcu3KfGVC34RRqKt8BCfpDn2tq9A@mail.gmail.com>
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	<CAKAnmm+yoNEQCV3qXceXm9rNoOAPYK0DQCpSqLkNGvGuOQ3W=A@mail.gmail.com>

On Wed, 2025-12-17 at 12:21 -0500, Greg Sabino Mullane wrote:
> On Wed, Dec 17, 2025 at 11:10 AM Colin 't Hart <[email protected]> wrote:
> > Thanks Laurenz, that confirms what I was assuming. Archiving is via pgbackrest
> > to a backup server, over SSH. Approx 750ms to archive each segment is crazy --
> > I'll check compression parameters too.
> 
> Switch to archive-async = on. When doing that, the typical time drops to 10ms or less.
> Also use a compress-type of lz4 or zst, which perform way better than the default gz.
> If you are encrypting, that's a bottleneck you just have to deal with, no shortcuts there. :)

I second that.  Asynchronous archiving in pgBackRest tends to work around the problem.

> tl;dr try other things before messing with the WAL size. The current size can work very
> well even on very large and very, very busy systems.

On the other hand, 16MB on a very busy system is somewhat ridiculous.
A somewhat bigger segment size may be appropriate.

Yours,
Laurenz Albe

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