A mirrored aggregate is a single WAFL storage file system with two physically separated and synchronously up-to-date copies on disks or array LUNs. These copies are called plexes. Data ONTAP typically names the first plex plex0 and the second plex plex1.
Each plex is a physical copy of the same WAFL file system, and consists of one or more RAID groups. As SyncMirror duplicates complete WAFL file systems, you cannot use the SyncMirror feature with a FlexVol volume—only aggregates (including all contained FlexVol volumes) are supported.