Added the 4th disks but it is not RAID1

Thank you everybody for your clarifications,

I don't really understand how xraid2 works...

I have 4x3to disks and 8.1tb of space, so 3 disks are used and 1 for redundancy right ?

But what is this redundancy disk ? It has only partial datas in it ? It can't save 8tb on 3tb so what happened if one of the 3 disks died ?

I understand that i need to backup my data on a removable hdd, that's what i planned to do but i choosed raid1 in first instancez because i thought if one disk die i just need to buy another one and replace in the bay.

So why xraid2 is better if i can loose my datas easier ?

Explain me please because i don't have enough disk space to save my datas, and reformat everything in the nas, i need a good reason to stay in this mode.

Also, which disk is the redundant one now in x-raid2 ? which number is the redundant disk ? If i remove it when nas is on, what happened ? Because i want to use it to backup my files before reset factory the nas.

Thanks guys,