Displaying Storage Pool Virtual Device Information

Each storage pool contains one or more virtual devices. A virtual
device is an internal representation of the storage pool that describes
the layout of physical storage and the storage pool's fault characteristics.
As such, a virtual device represents the disk devices or files that are used
to create the storage pool. A pool can have any number of virtual devices
at the top of the configuration, known as a top-level vdev.

If the top-level virtual device contains two or more physical devices,
the configuration provide data redundancy as mirror or RAID-Z virtual devices.
These virtual devices consist of disks, disk slices, or files. A spare is
a special virtual dev that tracks available hot spares for a pool.

The following example shows how to create a pool that consists of two
top-level virtual devices, each a mirror of two disks:

# zpool create tank mirror c1d0 c2d0 mirror c3d0 c4d0

The following example shows how to create pool that consists of one
top-level virtual device of four disks:

# zpool create mypool raidz2 c1d0 c2d0 c3d0 c4d0

You can add another top-level virtual device to this pool by using the zpool add command. For example:

# zpool add mypool raidz2 c2d1 c3d1 c4d1 c5d1

Disks, disk slices, or files that are used in nonredundant pools function
as top-level virtual devices. Storage pools typically contain multiple top-level
virtual devices. ZFS dynamically stripes data among all of the top-level virtual
devices in a pool.

Virtual devices and the physical devices that are contained in a ZFS
storage pool are displayed with the zpool status command.
For example: