In order to keep my home file archive safe, I've bought a Synology NAS and configured it to use a Synology Hybrid RAID configuration. Now almost a year since I started feeling safe about the years of photos and other precious files, I've discovered that a lot of people on the Web discuss uninterrupted power supplies for Synology NAS's. Since a NAS can also work without disk fault-tolerance, I wonder: are there situations when this fool-proof configuration may fail? Doesn't RAID protect me against possible troubles? I don't care about the loss of files during writing. Only the files already on the NAS are important. I was looking for a quiet compact energy-efficient NAS and wouldn't like to have to double the footprint, noise and sleep-mode power consumption without a good reason.
I am looking for a technical explanation of why I may need a UPS if I use a RAID on a NAS. Thanks.