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help / color / mirror / Atom feedFrom: Ron Johnson <[email protected]>
To: pgsql-general <[email protected]>
Subject: Re: wal segment size
Date: Wed, 17 Dec 2025 12:23:15 -0500
Message-ID: <CANzqJaAXOGvS3sEN1o0xAkA1Ud0JmzBEuPSJiF0gOkVBgKFYog@mail.gmail.com> (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>
Adding this to ~/.ssh/config will almost totally eliminate the cost of ssh
authentication:
Host *
ControlMaster auto
#ControlPath /run/user/%i/%L_%r_at_%n:%p
ControlPath ~/.ssh/%L_%r_at_%n:%p
ControlPersist 5m
Pointing ControlPath to /run/user/%i is even faster, but it doesn't always
exist if you sudo into the postgres service account.
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.
>
> 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
>>
>
--
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> lobster!
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