Ubuntu server 14.04 RAID1 file manager does not see the partition, why?

Question

linux

I installed it according to the manual, in general everything went well, though it was not possible to use gpt, because it did not allow me to put the "bootable" label, although it loaded with UEFI, but that's not the point ... When breaking it down, I decided to set the swap, "/" - ext4, " home" is btrfs, "usr" -xfs, "mnt" -xfs and "opt" -xfs. I start, open MC and it shows me the folder of my user (generally logical), but nothing more. I started checking the status by executing the command cat /proc/mdstat , which said that everything is active. A more descriptive lsblk command found all the disks it created, but only "/", "mnt" and "opt" had labels. I've never dealt with RAID before, I don't know how to use the space. What commands need to be executed?