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From: Adrian Klaver <[email protected]>
To: 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 08:31:34 -0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAMon-aSkPs=N5GHJsOzLs5RKcrba3=ng_6HUEKZy1=1GJgCEqg@mail.gmail.com>
References: <CAMon-aQ8X7H7jCC6ggKm9Uzcu3KfGVC34RRqKt8BCfpDn2tq9A@mail.gmail.com>
	<[email protected]>
	<CAMon-aSkPs=N5GHJsOzLs5RKcrba3=ng_6HUEKZy1=1GJgCEqg@mail.gmail.com>

On 12/17/25 08:10, Colin 't Hart 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.

How much of that time is network travel?

What are the configuration settings for the archiving portion of pgBackRest?

> 
> 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] 
> <mailto:[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
> 


-- 
Adrian Klaver
[email protected]

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