Overview
XenServer uses the Corosync clustering stack through xapi-clusterd to manage cluster membership.
Clusters are required when using GFS2 shared storage repositories (SRs).
XenServer 8.4 use Corosync 2 and to support future improvements, XenServer introduces Corosync 3.
Corosync 2 and Corosync 3 are architecturally different and you cannot perform a direct Rolling Pool Upgrade (RPU) between these versions.
A manual upgrade path is available in XenServer 8.4 and must be completed before upgrading to a greater version.
Note:
If Corosync 2 remains active, the RPU plugin will block the upgrade from XenServer 8.4 to a greater version.
Improvements in Corosync 3
Corosync 3 provides:
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Improved reliability for clustered environments.
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Enhanced scalability and performance.
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Faster and more consistent membership handling.
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Modernized network communication model.