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From: Mukesh Tanuku <mukesh.postgres@gmail.com>
Date: Sat, 13 Jul 2024 11:32:53 +0530
Message-ID: <CAJzgB-E49Jm7eUfgLD+DxoxU5Zk5d6ZeTciPRC7jCem41txDEA@mail.gmail.com>
Subject: Re: Replication lag in Postgres
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: pgsql-general@lists.postgresql.org
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Thank you for the information Laurenz Albe

On Fri, Jul 12, 2024 at 9:13=E2=80=AFPM Laurenz Albe <laurenz.albe@cybertec=
.at>
wrote:

> On Fri, 2024-07-12 at 20:41 +0530, Mukesh Tanuku wrote:
> > I have a question with postgres HA setup.
> > We are setting up a 2 node postgres cluster with async streaming
> replication, we want to
> > define a RPO (Recovery point objective) in case of primary failure.
> >
> > How can we best define the RPO in this setup? since it's an async
> streaming replication
> > setup there might be a chance of data loss which is proportional to the
> replication delay.
> >
> > Is there any way we can configure the delay duration, like for example
> to make sure every
> > 10 mins the standby sync has to happen with primary?
>
> When there is a delay, it is usually because replay at the standby is
> delayed.
> The WAL information is still replicated.  You won't lose that information
> on
> failover; it will just make the failover take longer.
>
> Unless you have a network problem, you should never lose more than a
> fraction
> of a second.
>
> Yours,
> Laurenz Albe
>

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<div dir=3D"ltr">Thank you for the information Laurenz Albe<br></div><br><d=
iv class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Fri, Jul =
12, 2024 at 9:13=E2=80=AFPM Laurenz Albe &lt;<a href=3D"mailto:laurenz.albe=
@cybertec.at">laurenz.albe@cybertec.at</a>&gt; wrote:<br></div><blockquote =
class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px sol=
id rgb(204,204,204);padding-left:1ex">On Fri, 2024-07-12 at 20:41 +0530, Mu=
kesh Tanuku wrote:<br>
&gt; I have a question with postgres HA setup.<br>
&gt; We are setting up a 2 node postgres cluster with async streaming repli=
cation, we want to<br>
&gt; define a RPO (Recovery point objective) in case of primary failure.=C2=
=A0<br>
&gt; <br>
&gt; How can we best define=C2=A0the RPO in this setup? since it&#39;s an a=
sync streaming replication<br>
&gt; setup there might be a chance of data loss which is proportional to th=
e replication delay.=C2=A0<br>
&gt; <br>
&gt; Is there any way we can configure=C2=A0the delay duration, like for ex=
ample to make sure every<br>
&gt; 10 mins the standby sync has to happen with primary?=C2=A0<br>
<br>
When there is a delay, it is usually because replay at the standby is delay=
ed.<br>
The WAL information is still replicated.=C2=A0 You won&#39;t lose that info=
rmation on<br>
failover; it will just make the failover take longer.<br>
<br>
Unless you have a network problem, you should never lose more than a fracti=
on<br>
of a second.<br>
<br>
Yours,<br>
Laurenz Albe<br>
</blockquote></div>

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