<div dir="ltr"><u></u>
<div>
<p>Hi <span style="font-size:11.0pt">S Sathish S,</span></p>
<p><span style="font-size:11.0pt">If I remember correctly, pacemaker
nodes agree on keeping the feature set at the highest version
that all of them support.</span></p>
<p><span style="font-size:11.0pt">At start, you</span><span style="font-size:11.0pt"> run v2.1.6, and all nodes agree on
that. Then you upgrade one node to v3.0.1, and you have both
v3.0.1 and v2.1.6 running in the cluster. So the nodes agree on
whatever feature set v2.1.6 defines, because that is the higher
version they all support, and it all works fine. However, once
you turn the v2.1.6 node off, there are only v3.0.1 nodes in the
cluster. So they agree on whatever feature set v3.0.1 defines </span><span style="font-size:11.0pt">and bump feature
set to that version. If you start v2.1.6 node again, it cannot
connect to the cluster, because it doesn't support the new
feature set.</span></p>
<p><span style="font-size:11.0pt">In a summary, the situation you
describe looks like an expected behavior to me. It also matches
the behavior you expect: both nodes remain operational and
communicate with each other. Up until the point you reboot the
non-upgraded node, that is.</span></p>
<p><span style="font-size:11.0pt">To debug this, check pacemaker log
on the node which doesn't connect. See if there is a message
about incompatible feature set / versions.</span></p>
<p><span style="font-size:11.0pt">Pacemaker team can correct me if
I'm wrong.</span></p>
<p><span style="font-size:11.0pt">Regards,<br>
Tomas</span></p>
<p><span style="font-size:11.0pt"><br>
</span></p>
<div>Dne 12. 02. 26 v 5:50 S Sathish S via
Users napsal(a):<br>
</div>
<blockquote type="cite">
<div>
<p class="MsoNormal"><span style="font-size:11.0pt">Hi Team,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Any update
on below issue. <u></u>
<u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks and
Regards,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">S Sathish S<u></u><u></u></span></p>
<div>
<div style="border:none;border-top:solid #e1e1e1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">
S Sathish S <br>
<b>Sent:</b> 09 February 2026 16:19<br>
<b>To:</b> Cluster Labs - All topics related to
open-source clustering welcomed
<a href="mailto:users@clusterlabs.org" target="_blank"><users@clusterlabs.org></a><br>
<b>Cc:</b> Devakumar K <a href="mailto:devakumar.k@ericsson.com" target="_blank"><devakumar.k@ericsson.com></a><br>
<b>Subject:</b> Rolling upgrade failure: v2.1.6 node
cannot connect after upgrading peer to v3.0.1<u></u><u></u></span></p>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Hi Team,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Issue : We
are performing a rolling upgrade from Pacemaker v2.1.6 to
v3.0.1 in a two-node cluster.
</span><span lang="EN-US">According to the [Pacemaker 3.0
Changes documentation](
</span><a href="https://projects.clusterlabs.org/w/projects/pacemaker/pacemaker_3.0_changes/" target="_blank"><span style="font-family:"Segoe UI Emoji",sans-serif">⚡</span>
Pacemaker 3.0 Changes</a><span lang="EN-US"> ), rolling
upgrades from Pacemaker 2.0.0 and later should be supported
with minimal changes.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">However,
after upgrading the first node (Node 1) to Pacemaker 3.0.1,
the second node (Node 2) running Pacemaker 2.1.6 is unable
to connect to the cluster after reboot of node2. Pacemaker
fails to start on Node 2 with the error:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Error: error
running crm_mon, is pacemaker running?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> crm_mon:
Connection to cluster failed: Connection refused<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Expected
Behaviour:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">During a
rolling upgrade, both nodes should remain operational and
communicate with each other until the second node is
upgraded. The non-upgraded node (2.1.6) should continue to
function while the upgraded node (3.0.1) acts as DC.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Questions:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">1. Is this a
known limitation with the rolling upgrade path from 2.1.6 to
3.0.1?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">2. Are there
specific compatibility issues between Pacemaker 3.0.1 and
2.1.6 that prevent cluster communication?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">3. Are there
any additional logs or diagnostic information needed to
troubleshoot this issue?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Environment:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">- Cluster:
2-node RHEL 8 cluster with Corosync<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">- Node 1
(node1): Upgraded to Pacemaker 3.0.1-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">- Node 2
(node2): Running Pacemaker 2.1.6-1.el8 (not yet upgraded)<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Node 1
(node1) - Upgraded:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Pacemaker:
3.0.1-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Corosync:
3.1.10-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">PCS:
0.12.2-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1:
1.33-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">resource-agents:
4.17.0-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Node 2
(node2) - Not Upgraded:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Pacemaker:
2.1.6-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Corosync:
3.1.7-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">PCS:
0.10.19-2.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1:
1.25-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">resource-agents:
4.12.0-1.el8<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Node1:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">[root@node1
testadmin]# pcs status pcsd<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> node1:
Online<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> node2:
Online<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">[root@node1
testadmin]# pcs status<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Cluster
Summary:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> * Stack:
corosync (Pacemaker is running)<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> * Current
DC: node1 (version 3.0.1-1.el8-3.0.1) - partition with
quorum<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> * Last
updated: Sat Feb 7 11:39:00 2026 on node1<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> * Last
change: Sat Feb 7 11:22:01 2026 by hacluster via hacluster
on node1<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> * 2 nodes
configured<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> * 23
resource instances configured (2 DISABLED)<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span lang="DA" style="font-size:11.0pt">Node
List:<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="DA" style="font-size:11.0pt">
* Online: [ node1 ]<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="DA" style="font-size:11.0pt">
* OFFLINE: [ node2 ]<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="DA" style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Full List of
Resources:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> *
SNMP_node2 (ocf:pacemaker:ClusterMon): Stopped<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> *
SNMP_node1 (ocf:pacemaker:ClusterMon): Started
node1<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Daemon
Status:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> corosync:
active/enabled<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> pacemaker:
active/enabled<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> pcsd:
active/enabled<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">[root@node1
testadmin]# rpm -qa | egrep
"pcs|pacemaker|corosy|pacemak|resource-a|libknet"<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-lz4-plugin-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-zstd-plugin-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-crypto-plugins-all-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-libs-3.0.1-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pcs-0.12.2-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">corosynclib-3.1.10-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-bzip2-plugin-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-lzma-plugin-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-zlib-plugin-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-plugins-all-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-crypto-openssl-plugin-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-plugins-all-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-schemas-3.0.1-1.el8.noarch<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-cluster-libs-3.0.1-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-3.0.1-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">corosync-3.1.10-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-lzo2-plugin-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-crypto-nss-plugin-1.33-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">resource-agents-4.17.0-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-cli-3.0.1-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">[root@node1
testadmin]#<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Node2:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">[root@node2
testadmin]# pcs status<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Error: error
running crm_mon, is pacemaker running?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> crm_mon:
Connection to cluster failed: Connection refused<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">[root@node2
testadmin]# pcs status pcsd<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> node2:
Online<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> node1:
Online<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">[root@node2
testadmin]#<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">[root@node2
testadmin]# rpm -qa | egrep
"pcs|pacemaker|corosy|pacemak|resource-a|libknet"<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-bzip2-plugin-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-zlib-plugin-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-crypto-openssl-plugin-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-schemas-2.1.6-1.el8.noarch<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-2.1.6-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">corosync-3.1.7-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-lz4-plugin-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-lzo2-plugin-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-zstd-plugin-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-crypto-nss-plugin-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-crypto-plugins-all-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">resource-agents-4.12.0-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-libs-2.1.6-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-cli-2.1.6-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pcs-0.10.19-2.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">corosynclib-3.1.7-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-lzma-plugin-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-compress-plugins-all-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">libknet1-plugins-all-1.25-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">pacemaker-cluster-libs-2.1.6-1.el8.x86_64<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks and
Regards,<br>
S Sathish S<u></u><u></u></span></p>
</div>
<br>
<fieldset></fieldset>
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</blockquote>
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</div>