I bought a DNS-320 yesterday and put 2 Seagate Barracuda (ST20000DM001) 2Tb drives in it. Set for mode 1 RAID. Updated firmware to 2.03b01. Left it doing a backup overnight, in the morning, I was unable to open my mapped drive. Opened the web interface and it said "None Hard Drives.". Log is full of "Fan Is Unable To Spin Or Fan Doesn't Exist" with a "Right Hard Drive Has Been Removed" and "Left Hard Drive Has Been Removed".
Tried reseating the hard drives, rebooting, downgraded the firmware to 2.02. Nothing. No hard drive lights on the front. It appears the power to the fan and the hard drives is no longer functional. I'm taking it in to exchange today. Hopefully the next one will be better, but it doesn't look good for reliability as a backup system if the unit itself only lasts for 6h.