====== ZFS - Structure - Device ======

A device is just a random-access block device.

  * vdevs are made of individual devices, and the zpool is made of vdevs.
  * Anything with a descriptor in /dev that allows random access will work.

vdevs can be built from:

  * Disks - The most common block devices. 
  * Entire hardware RAID arrays can used as individual devices.
  * Simple raw files.
    * Test pools made of sparse files are an incredibly convenient way to practice zpool commands, and see how much space is available on a pool or vdev of a given topology.