Historically, file systems have been constrained to one device and thus to the size of that device. Creating and re-creating traditional file systems because of size constraints are time-consuming and sometimes difficult. Traditional volume management products help manage this process.
Because ZFS file systems are not constrained to specific devices, they can be created easily and quickly, similar to the way directories are created. ZFS file systems grow automatically within the disk space allocated to the storage pool in which they reside.
Instead of creating one file system, such as /export/home, to manage many user subdirectories, you can create one file system per user. You can easily set up and manage many file systems by applying properties that can be inherited by the descendent file systems contained within the hierarchy.
For an example that shows how to create a file system hierarchy, see Creating a ZFS File System Hierarchy.