[ClusterLabs] Autostart/Enabling of Pacemaker and corosync

[damiano giuliani]

Thanks for the clarifications guys!

Il giorno mar 27 apr 2021 alle ore 18:24 Jehan-Guillaume de Rorthais <
jgdr at dalibo.com> ha scritto:

> On Mon, 26 Apr 2021 18:04:41 +0000 (UTC)
> Strahil Nikolov <hunter86_bg at yahoo.com> wrote:
>
> > I prefer that the stack is auto enabled. Imagine that you got a DB that
> is
> > replicated and primary DB node is fenced. You would like that node to
> join
> > the cluster and if possible to sync with the new primary instead of
> staying
> > down.
>
> In the case of PostgreSQL, the failing primary may not be able to failback
> automatically with the new primary. Worse, if it actually enters in
> replication, it might just silently become a corrupted standby, giving a
> wrong
> feeling of safety, until a new failover occurs.
>
> PAF doesn't handle auto-failback (eg. pg_rewind) per design, to avoid code
> complexity. We don't want to give a wrong feeling of perfect
> full-availability/failback/fully-automated-admin'ed PgSQL cluster. If
> something
> went wrong with your DB, you better need to check and fix it. You need both
> system and DBA guy on board to take care of the availability and safety of
> your
> cluster.
>
> Note that auto-failback of secondary nodes is safe, as far as they are able
> to actually follow up with the production. Maybe we can imaginer some
> safety
> belts in PAF's code to allow Pacemaker auto-start on boot, but refuse
> to start a badly shaped PostgreSQL.
>
> > One such example is the SAP HANA DB. Imagine that the current primary
> > node looses storage and it failed to commit all transactions to disk.
> Without
> > replication you will endure data loss for the last 1-2 minutes (depends
> on
> > your monitoring interval) unless you got a replication.
>
> PAF is a shared-nothing approach, it requires replication between nodes.
>
>
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