Another +1 for synology
Been using their products for 7ish years from the 2bay home units to the mid size office rack-mount units. They have technology similar to Drobo's 'Beyond Raid' called
Snology Hybrid Raid (SHR) Just make sure you read up and understand how those 'Size don't matter' raid technologies work...
I've chose synology over qnap and drobo mainly because of features and expandability. Currently have a
DS1812+ loaded to 18tb(6 drives) with some ISCSI and VMs running off it. I know in the near future I'll grow to needing 1 of the
DX513 expansion modules.
Friend of mine here in Afghanistan as about 5-8 units in service, no issues and that is in a dusty environment with generator power and moderate AC.