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 logical size) from the free space of its containing aggregate. This space is used to store the volume's 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 .005 × its logical size.
FlexVol volumes and traditional volumes have different best practices, optimal configurations, and performance characteristics. Make sure you understand these differences and deploy the configuration that is optimal for your environment.
For information about deploying a storage solution with FlexVol volumes, including migration and performance considerations, see Technical Report 3356 Introduction to Data ONTAP Release 7G at http://www.netapp.com/library/tr/3356.pdf.