I've chugged along with a second generation Drobo for at least five years. At first I was quite happy with it as all I wanted was some spacious local storage for audio and video files, plus backups of my computers. I threw a few 2TB Western Digital Green drives in it, figured out the hack to create a .sparsebundle file that works with Apple's Time Machine backup, stored all my iTunes files on it, and got on with life.
After a few years it started acting flaky, sending out email alerts about failed drives--but then a half-hour later announcing all was good. It was more than a full year later that a drive finally did fail, but the Drobo had quit sending warnings by then so the failure was a surprise. (I attributed the problem more to the heat in the un-air conditioned house I was living in at the time, than to any fundamental problem with the Drobo itself.) I didn't lose any data, Western Digital RMA'd my drive and sent me a 3GB drive as a free warranty replacement, so no complaints. Except...
It was slow.
Even with a FireWire 800 connection it had always been a little pokey, but I expected that with the Green drives. But the Drobo seems to have gotten slower and slower over the years, and eventually I started having problems with the Drobo Dashboard software. It'd say there was a newer version available, I'd install it, and then the newer version would say that it didn't support my Drobo, and it was a real pain to revert back to an older version. Then with enough upgrades of OS X the Drobo no longer appeared as a volume on the desktop, but it'd still appear as a volume at the top level in the Finder. Usually. Sometimes it'd just quit responding, locking up the Finder and forcing me to power cycle it.
So with performance dropping through the floor, questionable reliability, and software support likely to completely fail with some release of OS X in the near future, it looked like it was time to upgrade to newer hardware.
Synology seems to get good reviews almost everywhere, and unlike Drobo they've fully embraced the NAS concept for their smaller products and have a much wider variety of applications that can run. They also do a good job of supporting MacOS, and are comparable in price, so I figured I'd give them a try.
I ordered a DS414 and a couple 6TB HGST NAS drives. Setup was super easy--the screw-less disk trays are a nice feature, and the DiskStation web interface for managing it is quite easy to use. It took just a couple of minutes for the DS414 to automatically format the two drives using their SHR format (really RAID 1 behind the scenes for a two-drive configuration), and by then the DiskStation had found a software update that it was ready to download and install. A quick reboot later and my NAS was up to date and fully configured. I ran the built-in security audit and tweaked a few things to make it more secure, and then was ready to transfer the data off the Drobo and onto the DS414.
The first terabyte or so of data came across my gigabit Ethernet LAN at 8-10 MB/s, so that only took about 10 hours. Then I found the Drobo's Achilles heel: my collection of ripped CDs. I have almost 500 GB of ripped audio files, and for some reason those dropped the transfer rate to around 2.5 MB/s, so a transfer that should have taken about four hours has taken nearly 20 hours to complete. (Yes, it's still in the final stages of completing as I write this.)
I'll be happy to move on from the Drobo. Lord knows how long it'll take to securely wipe the drives, but I figure I can get $100 or so off the old hardware once that's done.
Now with the new Apple TV that was just announced, it looks like tvOS will be open enough that I might finally be able to skip the transcoding of video files. Nirvana!