In this article ,we will see the difference between Redhat cluster 6.x (Red Hat Enterprise Linux High Availability Add-On Release 6) and Redhat Cluster 7.x releases (Red Hat Enterprise Linux High Availability Add-On Release 7). In RHEL7 onwards “pacemaker” is the default cluster resource manager. Corosync is open source cluster engine which is responsible to manage the cluster interconnect and maintains the same cluster configuration across all the cluster nodes. All the configuration changes will be replicated to other node using corosync cluster engine. Pacemaker and Corosync are powerful open source technologies that completely replaces the CMAN and RGManager technologies from previous Redhat cluster releases. Pacemaker has completely simplified the the cluster configuration and administration.
Note: Pacemaker was shipping from REHL 6 onwards but not used widely since ccs /crm was part of it.
Cluster configuration file locations :
| Redhat Cluster Releases | Configuration files | Description |
| Prior to Redhat Cluster 7 | /etc/cluster/cluster.conf | Stores all the configuration of cluster |
| Redhat Cluster 7 (RHEL 7) | /etc/corosync/corosync.conf | Membership and Quorum configuration |
| Redhat Cluster 7 (RHEL 7) | /var/lib/heartbeat/crm/cib.xml | Cluster node and Resource configuration. |
Commands:
| Configuration Method | Prior to Redhat Cluster 7 | Redhat Cluster 7 (RHEL 7) |
| Command Line utiltiy | ccs | pcs |
| GUI tool | luci | PCSD – Pacemaker Web GUI Utility |
Services:
| Redhat Cluster Releases | Services | Description |
| Prior to Redhat Cluster 7 | rgmanager | Cluster Resource Manager |
| Prior to Redhat Cluster 7 | cman | Manages cluster quorum and cluster membership. |
| Prior to Redhat Cluster 7 | ricci | To provide access to luci web-Interface. |
| Redhat Cluster 7 (RHEL 7) | pcsd.service | Cluster Resource Manager |
| Redhat Cluster 7 (RHEL 7) | corosync.service | Manages cluster quorum and cluster membership. |
Cluster user:
| User Access | Prior to Redhat Cluster 7 | Redhat Cluster 7 (RHEL 7) |
| Cluster user name | ricci | hacluster |
How simple to create a cluster on RHEL 7 ?
| Redhat Cluster Releases | Cluster Creation | Description |
| Prior to Redhat Cluster 7 | ccs -h node1.ua.com –createcluster uacluster | Create cluster on first node using ccs |
| Prior to Redhat Cluster 7 | ccs -h node1.ua.com –addnode node2.ua.com | Add the second node to the existing cluster |
| Redhat Cluster 7 (RHEL 7) | pcs cluster setup uacluster node1 node2 | Create a cluster on both the nodes using pcs |
Is there any pain to remove a cluster in RHEL 7 ? No. It’s very simple.
| Redhat Cluster Releases | Remove Cluster | Description |
| Prior to Redhat Cluster 7 | rm /etc/cluster/cluster.conf | Remove the cluster.conf file on each cluster nodes |
| Prior to Redhat Cluster 7 | service rgmanager stop; service cman stop; service ricci stop; | Stop the cluster services on each cluster nodes |
| Prior to Redhat Cluster 7 | chkconfig rgmanager off; chkconfig cman off; chkconfig ricci off; | Disable the cluster services from startup |
| Redhat Cluster 7 (RHEL 7) | pcs cluster destroy | Destroy the cluster in one-shot using pacemaker |
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