The output in the image you attached isn't necessarily showing you what you think it is. The "megaraid_sas" bits aren't specifying any RAID level in the OS, they're specifying the use of the "megaraid_sas" driver to access the disk. Given that, you are very likely using a MegaRAID controller, which is capable of various RAID levels, but to see the configuration you would need to be in the MegaRAID BIOS screen. That information usually isn't available from the OS. When configured for RAID-1, the MegaRAID card will hide the two physical disks from the system, and will present the kernel and OS with only a single disk device.
In short: check your MegaRAID BIOS configuration.