To use the storage provided by FlexVol volumes as effectively as possible, you need to understand the space management capabilities that help you balance overall available storage against required user and application storage needs.
The volume guarantee, also called space guarantee or just guarantee, determines how much space for the volume is preallocated from the volume's associated aggregate when the volume is created.
Reservations, also called space reservations, file reservations, or LUN reservations, determine whether space for a particular file or LUN is preallocated from the volume.
Fractional reserve, also called fractional overwrite reserve or LUN overwrite reserve, enables you to control the size of the overwrite reserve for a FlexVol volume.
Automatic free space preservation can either increase the size of a volume or delete Snapshot copies to prevent a volume from running out of space—all without operator intervention.
These capabilities are used together to enable you to determine, on a volume-by-volume basis, whether to emphasize storage utilization, ease of management, or something in between.