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CAA (Cluster Aware AIX)

CAA is an AIX feature, and with that AIX kernel has the capability to provide specific cluster services, like heartbeating and node monitoring. Beside these, using Cluster Aware AIX you can easily create a cluster of AIX nodes. CAA does not replace PowerHA, it provides several services for PowerHA. PowerHA 7.1 and RSCT use the built-in AIX clustering capabilities, which simplifies the configuration and management of cluster.

CAA needs the following ports on all nodes for network communication:
4098 (for multicast)

These CAA commands can be used for managing clusters:

lscluster       list cluster configuration information
-c             cluster configuration
-d             disk (storage) configuration
-i             interfaces configuration
-m             node configuration
mkcluster       create a cluster
chcluster       change a cluster configuration
rmcluster       remove a cluster configuration
clcmd           run a command on all nodes of a cluster


PowerHA uses a shared disk to store Cluster Aware AIX (CAA) information. At least a 512 MB (and no more than 460 GB) shared disk is needed, for this cluster repository disk. (This disk cannot be used for application storage or any other purpose.)

CAA stores the repository disk related information in the ODM CuAt, as part of the cluster information.

# odmget CuAt | grep -p cluster
        name = "cluster0"
        attribute = "node_uuid"
        value = "52a6b8be-fff8-11e5-8e37-56a1a7627864"
        type = "R"
        generic = "DU"
        rep = "s"
        nls_index = 3

        name = "cluster0"
        attribute = "clvdisk"
        value = "d7063c81-3f64-b5f7-d82b-fa8ed99bfe61"
        type = "R"
        generic = "DU"
        rep = "s"
        nls_index = 2

In case this ODM entry is missing (which can cause that a node will fail to join the cluster) it can be repopulated (and the node forced to join the cluster) using clusterconf command:

clusterconf -r hdisk# <--hdisk# is the repository disk



  1. One question. How do you varyoff a "caavg_private" VG without messing up the cluster. I need to UPDATE SDDPCM and I am not sure if removing the cluster will be a good choiche.

    1. This comment has been removed by the author.

  2. You can varyoff CAA (caavg_private) using 'clctl -stop -n CLUSTERNAME -m NODENAME'
    Use "clctl -start -n CLUSTERNAME -m NODENAME" to varyon. (Try this command from the other node of cluster if you are facing problem with varyon on problematic node.)