Historically, file systems have been constrained to one device so that the file systems themselves have been constrained to the size of the device. Creating and re-creating traditional file systems because of size constraints are time-consuming and sometimes difficult. Traditional volume management products helped 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 space allocated to the storage pool.
Instead of creating one file system, such as /export/home, to manage many user subdirectories, you can create one file system per user. In addition, ZFS provides a file system hierarchy so that you can easily set up and manage many file systems by applying properties that can be inherited by file systems contained within the hierarchy.
For an example of creating a file system hierarchy, see Creating a ZFS File System Hierarchy.