There are some critical difference betwo the above type of volume in NetApp FAS.“Traditional volume is the collection of physical disk space whose entire contents is used to support a single volume.”
“A flexible volume, or FlexVol, is the collection of disk space allocated as a subset of the available space within an aggregate.”
IBM Redbooks – System Storage N series
So, the difference between is the space allocation type. A traditonal volume is based on how much disks being assigned to the volume. It’s impossible to reduce the space in a traditional volume, but a FlexVol has the ability. The minimum space of a FlexVol is 20MB, it might be increase or decrease based on the purpose of the volume.