Disks supported by PowerHA SystemMirror

Enhanced concurrent mode disks

The AIX® operating system supports enhanced concurrent mode. In enhanced concurrent mode, instances of the Concurrent Logical Volume Manager (CLVM) coordinate changes between nodes through the Group Services component of the Reliable Scalable Cluster Technology (RSCT) facility in AIX. Group Services protocols flow over the communications links between the cluster nodes.

With enhanced concurrent mode:

• Any disk supported by PowerHA SystemMirror for attachment to multiple nodes can be included in an enhanced concurrent mode volume group.
• Enhanced concurrent mode volume groups require the Concurrent Resource Manager. This provides the cluster initialization that is needed for CLVM to provide enhanced concurrent mode support.

Serial access mode disks

Only one node at a time can access serially accessed disks in read/write mode, and the shared volume groups residing on these disks can be varied on only one node in a cluster. The LVM perceives these disks as normal disks. The actual hdisks as perceived by the LVM can be either physical spindles (a configuration sometimes referred to as JBOD (Just a Bunch of Disks) to contrast it with RAID) or RAID disks. For JBOD configurations, configure the LVM to provide mirroring for data reliability.