[ClusterLabs] Antw: [EXT] Re: how to setup single node cluster

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Thu Apr 8 03:28:11 EDT 2021

>>> Reid Wahl <nwahl at redhat.com> schrieb am 08.04.2021 um 08:32 in Nachricht
<CAPiuu9-uEY_8JoDvT-p4NfNu8LzVkogyRx=uzMTz0yF--+rXjw at mail.gmail.com>:
> On Wed, Apr 7, 2021 at 11:27 PM d tbsky <tbskyd at gmail.com> wrote:
>> Reid Wahl <nwahl at redhat.com>
>> > I don't think we do require fencing for single-node clusters. (Anyone at
>> Red Hat, feel free to comment.) I vaguely recall an internal mailing list
>> or IRC conversation where we discussed this months ago, but I can't find it
>> now. I've also checked our support policies documentation, and it's not
>> mentioned in the "cluster size" doc or the "fencing" doc.
>>    since the cluster is 100% alive or 100% dead with single node, I
>> think fencing/quorum is not required. I am just curious what is the
>> usage case. since RedHat supports it, it must be useful in real
>> scenario.
> Disaster recovery is the main use case we had in mind. See the RHEL 8.2
> release notes:
>   -
> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/htm 
> l/8.2_release_notes/rhel-8-2-0-release#enhancement_high-availability-and-clus
> ters

I wonder: How does desaster recovery look like if a plane crashed into your single-node of the cluster?
(Without a cluster you would have some off-site backup, and probably some spare hardware off-site, too)
HA in that case is really interesting, as setting up the new hardware has to be done manually...

> I thought I also remembered some other use case involving MS SQL, but I
> can't find anything about it so I might be remembering incorrectly.
> -- 
> Regards,
> Reid Wahl, RHCA
> Senior Software Maintenance Engineer, Red Hat
> CEE - Platform Support Delivery - ClusterHA

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