To support the differing security, backup, performance, and data sharing needs of your users, you group the physical data storage resources on your storage system into one or more aggregates. These aggregates provide storage to the volume or volumes that they contain.
Each aggregate has its own RAID configuration, plex structure, and set of assigned disks. When you create an aggregate without an associated traditional volume, you can use it to hold one or more FlexVol volumes—the logical file systems that share the physical storage resources, RAID configuration, and plex structure of that common containing aggregate. When you create an aggregate with its tightly-bound traditional volume, then it can contain only that volume.