From: Laurenz Albe <laurenz.albe@cybertec.at>
To: norbert poellmann <np@ibu.de>
To: pgsql-admin@lists.postgresql.org
Subject: Re: Would you ever recommend Shared Disk Failover for HA?
Date: Fri, 23 Feb 2024 08:02:04 +0100
Message-ID: <32d1035973ed0c7be36a419df1246f94efae3166.camel@cybertec.at> (raw)
In-Reply-To: <20240222185937.M23609@ibu.de>
References: <20240222185937.M23609@ibu.de>
On Thu, 2024-02-22 at 20:34 +0100, norbert poellmann wrote:
> 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
>
> But [...]
>
> 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.
>
> Would you share your opinions or practical business experiences on this topic?
Back in the old days, we had special hardware devices for STONITH.
Anyway, my personal experience with a shared disk setup is a bad one.
Imagine two nodes, redundantly attached to disks mirrored across data
centers with fibrechannel. No single point of failure, right?
Well, one day one of the fibrechannel cables had intermittent failures,
which led to a corrupted file system.
So we ended up with a currupted file system, nicely mirrored across
data centers. We had to restore the 3TB database from backup.
Yours,
Laurenz Albe
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To: pgsql-admin@postgresql.org
Cc: laurenz.albe@cybertec.at, np@ibu.de, pgsql-admin@lists.postgresql.org
Subject: Re: Would you ever recommend Shared Disk Failover for HA?
In-Reply-To: <32d1035973ed0c7be36a419df1246f94efae3166.camel@cybertec.at>
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