I just wanted to follow up here with my experience with the Areca 5026.
HOLY !@#. I couldn't be happier. Ok, maybe if it were a little more quiet but it's not bad. A little louder than my Synology DS1511+ was.
Before I ordered the Areca, I decided to give a $350 Dyconn Quartz 5-bay USB 3.0 HW RAID enclosure a try. Miserable. Barely over 200MB/s with all 5 bays full and RAID 5. And that was purely sequential read/write with no other I/O. Throw anything random at it and it falls on its face, performs worse than a single USB3 HDD.
I was hesitant to go with the Areca 5026 because it's "only" 4 bays and I really wanted 5, but the choices were 4 or 8 and the 8 was more than I wanted to spend.
So, I put 4x3TB Seagate Barracuda drives into the Areca, told it RAID5, 64KB stripe size, write-back cache (Connected to a UPS).
Blackmagic reports 612MB/s write and 483MB/s read. AJA is also in that ballpark. That...that's faster than my SSD!
Some things to note with the Areca:
The RAID configuration is saved on the disks and NOT the controller. This means that you CAN move all of the drives into a new enclosure in ANY order and it will bring the array back online. The manual specifically mentions this in case there is a fault with the controller and it needs to be replaced. This is great news.
There is also online RAID expansion and conversion, it's just not the same as the Drobo thin provisioning. The RAID expansion would be if you had 2 drives and added a 3rd drive or more, then you could add the new drive(s) to the existing array and expand it out.
I know this thread is about the Drobo, but I wanted to follow up on my previous post(s) as well as address some potential confusion or misinformation about some hardware RAID solutions out there.