[ClusterLabs] Why Do Nodes Leave the Cluster?

[Strahil Nikolov]

On February 6, 2020 7:35:53 PM GMT+02:00, Eric Robinson <eric.robinson at psmnv.com> wrote:
>Hi Nikolov --
>
>> Defaults are 1s  token,  1.2s  consensus which is too small.
>> In Suse, token is 10s, while consensus  is 1.2 * token -> 12s.
>> With these settings, cluster  will not react   for 22s.
>>
>> I think it's a good start for your cluster .
>> Don't forget to put  the cluster  in maintenance (pcs property set
>> maintenance-mode=true) before restarting the stack ,  or  even better
>- get
>> some downtime.
>>
>> You can use the following article to run a simulation before removing
>the
>> maintenance:
>> https://www.suse.com/support/kb/doc/?id=7022764
>>
>
>
>Thanks for the suggestions. Any thoughts on timeouts for DRBD?
>
>--Eric
>
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Hi Eric,

The timeouts can be treated as 'how much time to wait before  taking any action'. The workload is not very important (HANA  is something different).

You can try with 10s (token) , 12s (consensus) and if needed  you can adjust.

Warning: Use a 3 node cluster or at least 2 drbd nodes + qdisk. The 2 node cluster is vulnerable to split brain, especially when one of the nodes  is syncing  (for example after a patching) and the source is fenced/lost/disconnected. It's very hard to extract data from a semi-synced  drbd.

Also, if you need guidance for the SELINUX, I can point you to my guide in the centos forum.

Best Regards,
Strahil Nikolov