diskutil

show disk information

show information of each disk:
diskutil list

create new RAID set:
createRAID mirror|stripe|concat setName format devices ...
ex: diskutil createRAID mirror MyArray JHFS+ disk2s4 disk2s5

Started RAID setup operation on disk disk2s4 Data_2_1
Adding booter for RAID partition 'disk2s4 Data_2_1'
Adding booter for RAID partition 'disk2s5 Data_2_2'
Adding disk 'disk2s4 Data_2_1' to new RAID set
Adding disk 'disk2s5 Data_2_2' to new RAID set
Creating RAID set (
disk2s4 Data_2_1,
disk2s5 Data_2_2
)
Bringing RAID partitions online
Waiting for new RAID to come online "C36FAD58-EF80-4DC7-AA4E-BAA85F15A222"
Creating file system on RAID volume "disk3"
[ + 0%..10%..20%..30%..40%..50%..60%..70%..80%..90%..100% ]
Finished RAID setup operation on disk disk3 MyArray