CentOS

From what you write it looks like it came with two preconfigured
RAID 0, /dev/sda (4 disks) and /dev/sdb (5 disks). RAID 0 has no
redundancy, so if one disk fails all data are lost. Depending on
on your usage it may be better to do a hardware reconfiguration
to RAID 5 or 6.

Edit: Is /dev/sdc two disks setup as RAID 1 (mirror)? If not, then
you have no redundancy on your system disk.

Great, Thank you so much. One question:
I have mounted the disks using UUID and added it on /etc/fstab.

How do I check if disks are mounted PERMANENTLY?

umount them then run mount -a and see if they come back.