You cannot convert directly from a traditional volume to a FlexVol volume. You must create a new FlexVol volume and then move the data to the new volume.
FlexVol volumes have best practices, optimal configurations, and performance characteristics different from those of traditional volumes. Make sure you understand these differences by referring to the available documentation on FlexVol volumes. Deploy the configuration that is optimal for your environment.
In addition, if your target volume is on the same storage system as the source volume, ensure that your system has enough free space to contain both copies of the volume during the migration.
If you are using this procedure to migrate your root volume, observe the notes specific to root volume migration.
If you want to migrate from a FlexVol volume to a traditional volume, you follow the same basic procedure, with the volume types reversed.