Creating a Mirrored Storage Pool
To create a mirrored pool, use the mirror keyword, followed by any number
of storage devices that will comprise the mirror. Multiple mirrors can be
specified by repeating the mirror keyword on the command line. The
following command creates a pool with two, two-way mirrors:
# zpool create tank mirror c1d0 c2d0 mirror c3d0 c4d0
The second mirror keyword indicates that a new top-level virtual device is
being specified. Data is dynamically striped across both mirrors, with data
being replicated between each disk appropriately.