mdadm reshaping

root:~# ls -la /raid-dev*
-rw-r--r-- 1 root root 524288000 Jul 10 17:02 /raid-dev1
-rw-r--r-- 1 root root 524288000 Jul 10 17:02 /raid-dev2
-rw-r--r-- 1 root root 524288000 Jul 10 17:02 /raid-dev3
-rw-r--r-- 1 root root 524288000 Jul 10 17:02 /raid-dev4
-rw-r--r-- 1 root root 524288000 Jul 10 17:02 /raid-dev5
-rw-r--r-- 1 root root 524288000 Jul 10 17:02 /raid-dev6

root:~# losetup -a
/dev/loop0: [0803]:12779 (/raid-dev1)
/dev/loop1: [0803]:12780 (/raid-dev2)
/dev/loop2: [0803]:12781 (/raid-dev3)
/dev/loop3: [0803]:12782 (/raid-dev4)
/dev/loop4: [0803]:12783 (/raid-dev5)
/dev/loop5: [0803]:12784 (/raid-dev6)

root:~# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md10 : active raid5 loop0[0] loop2[3] loop1[1]
      1022976 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]

root:~# mdadm --add /dev/md10 /dev/loop3
mdadm: added /dev/loop3
root:~# mdadm --add /dev/md10 /dev/loop4
mdadm: added /dev/loop4
root:~# mdadm --add /dev/md10 /dev/loop5
mdadm: added /dev/loop5

root:~# mdadm --grow /dev/md10 --raid-devices=6 --level=6
mdadm level of /dev/md10 changed to raid6
mdadm: Need to backup 2048K of critical section..

root:~# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md10 : active raid6 loop5[6] loop4[5] loop3[4] loop0[0] loop2[3] loop1[1]
      1022976 blocks super 1.2 level 6, 512k chunk, algorithm 18 [6/5] [UUU_UU]
      [===>.................]  reshape = 18.1% (92672/511488) finish=0.6min speed=11584K/sec

root:~# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md10 : active raid6 loop5[6] loop4[5] loop3[4] loop0[0] loop2[3] loop1[1]
      2045952 blocks super 1.2 level 6, 512k chunk, algorithm 2 [6/6] [UUUUUU]