Advanced Disk Partitioning (ADP) is a feature that enables ONTAP to partition a disk into multiple logical units and use them for different purposes. ADP has two main benefits for AFF or FAS systems:

It optimizes storage capacity by reducing the number of disks required for the root aggregates, which store the system and configuration data. By using ADP, the root aggregate can share the same disk with a data aggregate, which stores the user data. This frees up more disks for data aggregates and increases the usable space for data.

It reduces RAID parity overhead by creating smaller RAID groups with partitions instead of whole disks. This reduces the amount of parity data that needs to be written and read, which improves the performance and efficiency of the system.Reference=What are the rules for Advanced Disk Partitioning?,Considerations for automatic drive assignment and ADP systems in ONTAP 9.4 and later,NetApp AFF and Advanced Drive Partition v2, part 1