Stampatelo in mente!! Mirroring zpool/rpool

zpool attach [-f] pool device new_device

Attaches new_device to an existing zpool device. The
existing device cannot be part of a raidz configuration.
If device is not currently part of a mirrored configura-
tion, device automatically transforms into a two-way
mirror of device and new_device. If device is part of a
two-way mirror, attaching new_device creates a three-way
mirror, and so on. In either case, new_device begins to
resilver immediately.