I'm not sure on how to reply, because experiences with a Drobo seem to be extremely hit or miss and it is all very anecdotal. My drobo with all WD green drives is as silent as my Mac minis and MBP are, while a friend of mine has one also with similar drives that's so loud it's very difficult to sleep in the same room with it (and yes, it rivals his Mac Pro in terms of noise). I've not had a single problem with my dro…
Buffer I/O error on device sda1, logical block 422806282 scsi2 (0:0): rejecting I/O to dead device
SCSI error : return code = 0x70000 end_request: I/O error, dev sda, sector 4533105544
HFS+-fs: WARN: Turning journaling back on even though Journalling was not on at mount. HFS+-fs: WARN: We may be setting the Journal bit on an unjournalled filesystem but it is OK.
So please don't soften the issue — it fails. It failed for me multiple times already and I expect it to fail again.
I guess it's OK to use a Drobo if you get another one as backup for the first one — but then, what's the point?