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<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D;mso-fareast-language:EN-US">Hi!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;color:#1F497D;mso-fareast-language:EN-US">I cannot answer your questions actually, but there is a comnpromise with all timeouts:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;color:#1F497D;mso-fareast-language:EN-US">If it’s too long, you have an unnecessary service outage, but when it’s too short, you activate recovery mechanisms without actual need. With a sub-second
reaction time, you may have additional trouble.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;color:#1F497D;mso-fareast-language:EN-US">Just one example: In a SAN RAID storage a single disk with bad sectors caused significant read delays (while the disk retried reading and the controller
did not mark the disk as bad (in this case the timeout was too long, helping the vendor not to have to replace the disk). In such a case switching to another node accessing the same disks would not help…<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Mit kollegialen Grüßen<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Ulrich Windl<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Users <users-bounces@clusterlabs.org>
<b>On Behalf Of </b>Holger Haidinger <DE ERL SWD EM> via Users<br>
<b>Sent:</b> Friday, February 20, 2026 4:41 PM<br>
<b>To:</b> users@clusterlabs.org<br>
<b>Cc:</b> Holger Haidinger <DE ERL SWD EM> <Holger.Haidinger@fluenceenergy.com><br>
<b>Subject:</b> [EXT] [EXT] [ClusterLabs] Sub-second failover detection in Corosync/Pacemaker clusters - 2026 update?<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="color:black">Hi everyone,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">I'm revisiting a thread from 2015 (https://www.mail-archive.com/users@clusterlabs.org/msg00554.html) about achieving sub-second failover detection in HA clusters, and I'm curious about the current state of affairs
nearly a decade later.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">My Environment:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">- Corosync 3.1.6<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">- Pacemaker 2.1.2 <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">- Architecture: 2-node cluster + QDevice (also testing 3-node setups)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">- Network: Dedicated physical NIC for cluster traffic (low-latency requirements)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Specific Questions:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">1. With modern Corosync/Pacemaker versions, is sub-second fault detection and failover initiation realistically achievable in production environments?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">2. Are there any published measurements or community experiences showing the fastest stable failover times you've achieved? What's considered a reliable minimum time span?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">3. Have there been significant enhancements in the newer versions of Corosync and Pacemaker (post-2015) that specifically target detection speed and failover latency?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">4. If sub-second detection is possible, what are the key configuration parameters and potential trade-offs (false positives, network sensitivity, resource overhead)?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Thanks in advance!<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Holger Haidinger<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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