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.
Because a FlexVol volume is managed separately from the aggregate, you can create small FlexVol volumes (20 MB or larger), and you can increase or decrease the size of FlexVol volumes in increments as small as 4 KB.
When a FlexVol volume is created, it reserves a small amount of extra space (approximately 0.5 percent of its nominal size) from the free space of its containing aggregate. This space is used to store volume metadata. Therefore, upon creation, a FlexVol volume with a space guarantee of volume uses free space from the aggregate equal to its size × 1.005. A newly-created FlexVol volume with a space guarantee of none or file uses free space equal to 0.005 × its nominal size.