A plex is a collection of one or more Redundant Array of Independent Disks (RAID) groups that together provide the storage for one or more Write Anywhere File Layout (WAFL) file system aggregates or traditional volumes.
Data ONTAP uses plexes as the unit of RAID-level mirroring when the
SyncMirror software is enabled.
An aggregate is the physical layer of storage that consists of the disks within the RAID groups and the plexes that contain the RAID groups.
A traditional volume is directly tied to the underlying aggregate and its properties. When you create a traditional volume,
Data ONTAP creates the underlying aggregate based on the properties you assign with the
vol create command, such as the disks assigned to the RAID group and RAID-level protection.
A FlexVol volume is a volume that is loosely coupled to its containing aggregate. A FlexVol volume can share its containing aggregate with other
FlexVol volumes. Thus, a single aggregate can be the shared source of all the storage used by all the
FlexVol volumes contained by that aggregate.
You use either traditional or FlexVol volumes to organize and manage system and user data. A volume can hold qtrees and LUNs.
After you set up the underlying aggregate, you can create, clone, or resize FlexVol volumes without regard to the underlying physical storage. You do not have to manipulate the aggregate frequently.
A LUN is a logical unit of storage that represents all or part of an underlying physical disk.
