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From: Colin 't Hart <[email protected]>
To: Laurenz Albe <[email protected]>
Cc: PostgreSQL General <[email protected]>
Subject: Re: wal segment size
Date: Wed, 17 Dec 2025 17:10:19 +0100
Message-ID: <CAMon-aSkPs=N5GHJsOzLs5RKcrba3=ng_6HUEKZy1=1GJgCEqg@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAMon-aQ8X7H7jCC6ggKm9Uzcu3KfGVC34RRqKt8BCfpDn2tq9A@mail.gmail.com>
	<[email protected]>

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.

Any reason not to bump it up to 1GB? Or is that overkill?

/Colin

On Wed, 17 Dec 2025 at 16:25, Laurenz Albe <[email protected]> wrote:

> On Wed, 2025-12-17 at 16:13 +0100, Colin 't Hart wrote:
> > I see very little advice on tuning WAL segment size.
> >
> > One of my clients has a few datawarehouses at around 8 - 16 TB
> >
> > On one of the nodes there are approx 15000 WAL segments of 16MB each,
> totalling
> > approx 230GB. The archiver is archiving approx one per second, so approx
> 4 hours to clear.
> >
> > Would we gain anything by bumping the WAL segment size?
>
> Very likely yes, if the problem is the overhead of starting the
> archive_command.
>
> Another thing that can slow down archiving is if you compress these
> segments
> too aggressively.
>
> Yours,
> Laurenz Albe
>

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