I don't have experience with Drobo, but if you are looking for NAS for backup, I can say Synology works very well for home or small business use. You need to choose the product line such as DS712+, DS412+, or DS212+.
I'm a user of DS710+ (previous version of 712+), and it is really FAST.
Disk read/write benchmark shows almost 65-70MBps, which is comparable to the number of internal SATA drives.
Do I use it for audio drive? Yes, I tested and it works for streaming 50-60 tracks files (reaper), no problem. But it is a risky operation for audio, because somebody on the network start transferring big chunk of data, then disk read/write drops. It's a network "shared" drive, so you need to understand that aspect.
But for the archiving/backup purpose, with MULTIPE machines (maybe three or more), NAS is the best solution, IMO.