For entry-level platforms, All Flash FAS (AFF) platforms, and FAS platforms with only SSDs attached, aggregates can be composed of parts of a drive rather than the entire drive.
The root-data partitioning capability is usually enabled and configured by the factory. It can also be established by initiating system initialization using option 4 from the boot menu. Note that system initialization erases all data on the disks of the node and resets the node configuration to the factory default settings.
When a node has been configured to use root-data partitioning, partitioned disks have two partitions:
The smaller partition is used to compose the root aggregate. The larger partition is used in data aggregates. The size of the partitions is set by Data ONTAP, and depends on the number of disks used to compose the root aggregate when the system is initialized. (The more disks used to compose the root aggregate, the smaller the root partition.) After system initialization, the partition sizes are fixed; adding partitions or disks to the root aggregate after system initialization increases the size of the root aggregate, but does not change the root partition size.
The partitions are used by RAID in the same manner as physical disks are; all of the same requirements apply. For example, if you add an unpartitioned drive to a RAID group consisting of partitioned drives, the unpartitioned drive is partitioned to match the partition size of the drives in the RAID group and the rest of the disk is unused.
If a partitioned disk is moved to another node or used in another aggregate, the partitioning persists; you can use the disk only in RAID groups composed of partitioned disks.