Notice they have TWO of the two drives ... 4 total. I'm sure they're in RAID1, which is a direct copy, 1:1.
Other RAID options with redundancy include RAID 5 or RAID6. I use RAID6 on my 16-drive server. With so many drives, but still a need for very high capacity, I couldn't go with RAID1 because I'd have to give up 4TB of space, half. Instead, with RAID6 I only have to give up two drives to redundancy, which is 1TB. Of course this means that if two drives fail, I haven't lost anything. If a third does, I'm in huge trouble. On their end, if one fails, they're fine. If a second does, then they're in big trouble.
Don't forget that RAID is never an acceptable replacement for good backups so they surely have many backups. I'm curious if this server is onsite at their Minnesota offices. If so, that's pretty neat they host everything in-house. Secondly, they should have offsite backups to protect against the worst of the worst.