Message-ID: <1decdbcd01ae61fc7a96517e66eae3834751c49e.camel@lists.simkin.ca>
Subject: Re: Access a Postgres storage with two independent instances
From: Alan Hodgson <ahodgson@lists.simkin.ca>
To: pgsql-novice@lists.postgresql.org
Date: Tue, 07 May 2024 09:34:39 -0700
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On Tue, 2024-05-07 at 09:56 +0530, first last wrote:
> Actually what I want is=A0multiple Postgres=A0instances to have read
> and write access to the same data storage directory. Anyway, that
> can not be possible as what you=A0say. But, when I deploy
> MySQL/MongoDB deployment with multiple replicas to access the same
> storage, the all pods except one become=A0CrashLoopBackOff=A0state.
> This is happening for MySQL/Mongo. When it comes to Postgres, I
> deployed it with multiple pods, all the pods became healthy and
> there is no such=A0CrashLoopBackOff state occurred. But those pods
> access different storages for every pod. Why this totally different
> from MySQL and Mongo?

No idea, but this doesn't appear to have anything to do with
PostgreSQL. You could load any image in that container and then see
what the storage looks like. Probably better asked on a kubernetes
list somewhere.

Random thought, though, if you actually have multiple nodes in your
k8s cluster, you might just be seeing an artifact of the
ReadWriteOnce access mode. For a real shared volume you probably want
ReadWriteMany, which only a few storage backends support (and which,
again, PostgreSQL would not work on).

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</style></head><body><div>On Tue, 2024-05-07 at 09:56 +0530, first last wro=
te:</div><blockquote type=3D"cite" style=3D"margin:0 0 0 .8ex; border-left:=
2px #729fcf solid;padding-left:1ex"><div>Actually what I want is&nbsp;multi=
ple Postgres&nbsp;instances to have read and write access to the same data =
storage directory. Anyway, that can not be possible as what you&nbsp;say. B=
ut, when I deploy MySQL/MongoDB deployment with multiple replicas to access=
 the same storage, the all pods except one become&nbsp;CrashLoopBackOff&nbs=
p;state. This is happening for MySQL/Mongo. When it comes to Postgres, I de=
ployed it with multiple pods, all the pods became healthy and there is no s=
uch&nbsp;CrashLoopBackOff state occurred. But those pods access different s=
torages for every pod. Why this totally different from MySQL and Mongo?</di=
v></blockquote><div><br></div><div>No idea, but this doesn't appear to have=
 anything to do with PostgreSQL. You could load any image in that container=
 and then see what the storage looks like. Probably better asked on a kuber=
netes list somewhere.</div><div><br></div><div>Random thought, though, if y=
ou actually have multiple nodes in your k8s cluster, you might just be seei=
ng an artifact of the ReadWriteOnce access mode. For a real shared volume y=
ou probably want ReadWriteMany, which only a few storage backends support (=
and which, again, PostgreSQL would not work on).</div><div><span></span></d=
iv></body></html>

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