root@Knoppix:~$ sudo -s
root@Knoppix:~# modprobe md_mod
root@Knoppix:~# swapoff -a
root@Knoppix:~# dmsetup remove_all
root@Knoppix:~# dmsetup ls
No devices found
root@Knoppix:~# mdadm -A /dev/md0 /dev/sda3 /dev/sdb1 /dev/sdc1 /dev/sdd1
mdadm: /dev/md0 has been started with 4 drives.
root@Knoppix:~# mount /dev/md0 /media/test

# geom disk list
Geom name: ada2                                                                 
Providers:                                                                      
1. Name: ada2                                                                   
   Mediasize: 2000398934016 (1.8T)                                              
   Sectorsize: 512                                                              
   Stripesize: 4096                                                             
   Stripeoffset: 0                                                              
   Mode: r0w0e0                                                                 
   fwsectors: 63                                                                
   fwheads: 16

セクタ数(計算式): Mediasize: 2000398934016 ÷ Sectorsize: 512 ＝ 3907029168 Sector

# dd if=/dev/zero of=/dev/ada2 bs=512 count=1 seek=3907029167
1+0 records in                                                                  
1+0 records out                                                                 
512 bytes transferred in 0.000154 secs (3329432 bytes/sec)