Use one disk per node to place the devices used by that node. If the node has more than one data devices and the disk contention is observed, move one data device to another disk. The same applies to the history file as well.
Make sure that all data and log devices and all history files reside on local disks (not NFS-mounted or other remotely mounted disks).
If the monitoring tools still show contention on the HADB disks, the data buffer pool size can be increased.