Expanding storage in ZFS
In addition to being a filesystem, ZFS is a storage array and volume manager, meaning that you can feed it a whole pile of disk devices, not just one. The heart of a ZFS storage system is the zpool—this is the most fundamental level of ZFS storage. The zpool in turn contains vdevs, and vdevs contain actual disks within them. Writes are split into units called records or blocks, which are then distributed semi-evenly among the vdevs.
