Yes, they are built in, but I would advise against buying this product, it has very poor equipment, i.e. the NAS has extremely little RAM, it is only 512MB and unfortunately not very much is possible. Also not ideal, a NAS with fixed disks is a mess if the disk fails, because you have to shut it down and cannot change the disk during operation without tools. There are a lot of used 2-drive NASs like this, because many people unfortunately only realise after buying one that a Synology NAS with a j in its name isn't much use.

Also not optimal, in this configuration you buy 2 x 4 = 8TB but you give away 4TB with the RAID1 mirroring. If a 4TB disc breaks, you have to buy another one and have given away 4TB again. My recommendation would therefore be a 4-drive NAS, which is better in all respects and doesn't cost much more. You can then also install smaller disks and give away little space for redundancy. Of course, the 4-drive NAS is a little more expensive, but in return you get a NAS that is not a toy and can be used optimally over the years. And a NAS with more than 2 disks can also make use of the additional hardware protection of a RAID5, where a disk can break and the NAS still continues to run, you replace the defective disk during operation and the NAS will automatically reintegrate this disk into the RAID5.

I'd go for this one, it's very well ventilated, whisper quiet, has 2GB RAM and a Quad Core processor. You can also run more than just a backup on it:

Synology DS418

And then I would buy 3 x 2TB hard disks, they are not expensive and if one breaks, you only need to buy another cheap 2TB disk.

Seagate IronWolf (2 TB, 3.5", CMR)