ubuntu@ubuntu:/dev/md$ sudo cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md126 : active raid5 sdb[3] sdc[2] sdd[1] sde[0]
      11721048064 blocks super external:/md127/0 level 5, 64k chunk, algorithm 0 [4/4] [UUUU]
      [====>................]  resync = 24.2% (946865884/3907016064) finish=399.7min speed=123402K/sec

md127 : inactive sdb[3](S) sde[2](S) sdd[1](S) sdc[0](S)
      10080 blocks super external:imsm

unused devices: <none>

ubuntu@ubuntu:/dev/md$ sudo mount -t ntfs-3g /dev/md126 /tmp/hdd/
NTFS signature is missing.
Failed to mount '/dev/md126': Invalid argument
The device '/dev/md126' doesn't seem to have a valid NTFS.
Maybe the wrong device is used? Or the whole disk instead of a
partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around?