Setting up a PowerHA SystemMirror (formerly HACMP) cluster requires careful planning and execution to ensure high availability for critical applications. This guide walks through the steps to configure a two-node AIX cluster using shared storage and CAA (Cluster Aware AIX).
Note: In this guide, the primary (active) node is referred to as node1, and the secondary (passive) node is node2.
Step 1: Generate SSH Key Pair
On Node1 (repeat for Node2 if you want both directions):
# su - root
# ssh-keygen -t rsa -f /root/.ssh/id_rsa
Press Enter for default file location.
Leave passphrase empty (important for passwordless access).
Step 2: Copy Public Key to Other node
Use ssh-copy-id (if available) or manual copy:
On node1, view public key:
# cat /root/.ssh/id_rsa.pub
On node2, append it to /root/.ssh/authorized_keys:
# vi /root/.ssh/authorized_keys
# (paste the key from node1)
# chmod 600 /root/.ssh/authorized_keys
Step 3: Set Correct Permissions
On all nodes:
# chmod 700 /root/.ssh
# chmod 600 /root/.ssh/authorized_keys
# chmod 600 /root/.ssh/id_rsa
# chmod 644 /root/.ssh/id_rsa.pub
Step 4: Test Node-to-Node Communication
Test remote shell communication using clrsh:
# /usr/sbin/clrsh node1 hostname # Output: node1
# /usr/sbin/clrsh node2 hostname # Output: node2
If tests fail, the cluster cannot be created until the communication issue is resolved.
Step 5: Verify Shared Storage
Before creating a cluster, ensure all shared disks are visible on both nodes:
# lspv
Check all shared datavg hdisks and the hdisk intended for the CAA repository.
Ensure all shared hdisks have reserve_policy = no_reserve:
# lsattr -El hdiskXX
# chdev -l hdiskXX -a reserve_policy=no_reserve
The hdisk used for the CAA repository should be new and never part of a VG.
Step 6: Verify Network Interfaces
Run ifconfig -a on both nodes to identify boot IP addresses for all adapters.
At this stage, there should be no alias IPs configured.
Step 7: Configure rhosts for Cluster Communication
Add all boot IPs to /etc/cluster/rhosts on both nodes (one IP per line, no comments).
Ensure /etc/hosts resolves all IPs locally.
Configure /etc/netsvc.conf to prioritize local hostname resolution:
hosts=local4,bind4
Step 8: Restart Cluster Communication Daemon
# stopsrc -s clcomd; sleep 5; startsrc -s clcomd
Step 9: Install PowerHA
Mount NFS share both the nodes
Mount NFS share both the nodes
# mount nimserver1:/export/powerHA /mnt
Change to the PowerHA installation directory:
# cd /mnt/HA7.x/
Install all packages:
# installp -acgXYd . all
Step 10: Create the Cluster
On node1, add the cluster and nodes:
# /usr/es/sbin/cluster/utilities/clmgr add cluster <cluster_name> NODES="node1 node2"
Add a repository disk (disable validation for a new disk):
# /usr/es/sbin/cluster/utilities/clmgr add repository <Repository_Disk_PVID> DISABLE_VALIDATION=true
Synchronize the cluster configuration:
# /usr/es/sbin/cluster/utilities/clmgr sync cluster
Verify cluster status on both nodes:
# lscluster -m # Should show each node as UP
# lssrc -a | grep cthags # Should show cthags active
Step 11: Create Resource Group and Service IP
Create a resource group:
# /usr/es/sbin/cluster/utilities/clmgr add resource_group <RG_Name> NODES=node1,node2
Create a service IP:
# /usr/es/sbin/cluster/utilities/clmgr add service_ip <Service_IP_Label> NETWORK=<Network_Name>
Step 12: Create Shared Volume Group
# /usr/es/sbin/cluster/sbin/cl_mkvg -f -n -cspoc -n 'node1,node2' -r '<RG_Name>' -y '<VG_Name>' -V '<VG_Major_Number>' -E <hdiskx_PVID>
Step 13: Add Resources to Resource Group
# /usr/es/sbin/cluster/utilities/clmgr modify resource_group '<RG_Name>' SERVICE_LABEL='<Service_IP_Label>'
Step 14: Synchronize and Start Cluster
Synchronize the cluster:
# /usr/es/sbin/cluster/utilities/clmgr sync cluster
Start PowerHA and bring the cluster online:
# /usr/es/sbin/cluster/utilities/clmgr online cluster WHEN=now START_CAA=yes
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