vdev_create
spa->spa_root_vdev = vdev_create(guid, NULL);
vdev = vdev_create(guid, vdev_mirror_read);
vdev = vdev_create(guid, vdev_raidz_read);
vdev = vdev_create(guid, vdev_replacing_read);
vdev = vdev_create(guid, vdev_indirect_read);
vdev = vdev_create(guid, vdev_missing_read);
vdev = vdev_create(guid, vdev_disk_read);
(error = vdev_create(rvd, txg, B_FALSE)) == 0 &&
(error = vdev_create(vd, txg, B_FALSE)) != 0)
if ((error = vdev_create(newrootvd, txg, replacing)) != 0)
extern int vdev_create(vdev_t *, uint64_t txg, boolean_t isreplace);