[ClusterLabs] 2node cluster question

[Digimer]

On 2018-08-15 07:20 AM, Andrei Borzenkov wrote:
> On Wed, Aug 15, 2018 at 11:58 AM Stefan K <Shadow_7 at gmx.net> wrote:
>>
>> Hello,
>>
>> what is the 'best' 2-node cluster config?
> 
> There is no such thing :) Besides, your example does not include any
> resource which means it does nothing useful.

I'd argue that 2-node is the best config. Minimum complexity, and though
quorum is useful, it's not required.

>> What I want, if it run on nodeA and nodeA goes in standby or shut down, everything must start at nodeB,
> 
> This requires working fencing (STONITH) to avoid split brain. Your
> configuration requires STONITH but does not define any STONITH
> resource so fail-over won't work.

Exactly. Fencing is required (but this is true in 3+ clusters as well).

>> if nodeA comes back, everything must still run on nodeB.
>>
> 
> This is controlled by resource configuration, usually stickiness attribute.
> 
>> pacemaker looks like:
>>         have-watchdog=false \
>>         dc-version=1.1.16-94ff4df \
>>         cluster-infrastructure=corosync \
>>         cluster-name=zfs-vmstorage \
>>         no-quorum-policy=stop \
>>         stonith-enabled=true \
>>         last-lrm-refresh=1528814481
>> rsc_defaults rsc_defaults-options: \
>>         resource-stickiness=100
>>
>> and the corosync.config:
>> totem {
>>     version: 2
>>     secauth: off
>>     cluster_name: zfs-vmstorage
>>     transport: udpu
>>     rrp_mode: passive
>> }
>>
>> nodelist {
>>     node {
>>         ring0_addr: zfs-serv3
>>         ring1_addr: 192.168.251.1
>>         nodeid: 1
>>     }
>>
>>     node {
>>         ring0_addr: zfs-serv4
>>         ring1_addr: 192.168.251.2
>>         nodeid: 2
>>     }
>> }
>>
>> quorum {
>>     provider: corosync_votequorum
>>     two_node: 1
> 
> This fakes quorum, meaning no-quorum-policy setting is not really
> relevant - cluster will always have quorum, even if one node fails.
> 
>> }
>>
>> logging {
>>     to_logfile: yes
>>     logfile: /var/log/corosync/corosync.log
>>     to_syslog: yes
>> }
>>
>> thanks in advance
>> and best regards
>> Stefan


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