From: "norbert poellmann" <np@ibu.de>
To: pgsql-admin@lists.postgresql.org
Subject: Would you ever recommend Shared Disk Failover for HA?
Date: Thu, 22 Feb 2024 20:34:55 +0100
Message-Id: <20240222185937.M23609@ibu.de>
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Admins,

https://www.postgresql.org/docs/current/different-replication-solutions.html
is listing a shared disk solution for HA.

It also mentions, "that the standby server should never access the shared storage while the primary server is running."

In a datacenter, where we have postgresql servers running on vmware VMs, the shared disk configuration sounds like an appealing solution: simple configuration, single server at a given time, simple fail-over, fully non-or-nothing write mechanics, no hazzle with replication_slots during/after failover, etc...

But "Attempts to use PostgreSQL in multi-master shared storage configurations will result in extremely severe data corruption" (https://wiki.postgresql.org/wiki/Shared_Storage).


So it seems to me, getting the comfort of a single server solution, which, in a failover, gets replaced by another single server, is paid by getting the low risk of high damage.

I know of the provisions of fencing, STONITH, etc. - but in practise, what is a robust solution? 

For example: How can I STONITH a node while having network problems? 
Whithout reaching the host, I cannot shoot it, nor shut it. 
I also cannot wait for it get visible in the network again: another client might have interfered and commited a transaction upon the retired master server, faster than I can do some fencing/stonith or whatever.


Would you share your opinions or practical business experiences on this topic?

Thanks a lot

cheers

Norbert Poellmann

--
Norbert Poellmann EDV-Beratung             email  : np@ibu.de
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