How to improve IO performance of Drobo Gen 2?

I'm running a Late 2012 Mac mini Server, with macOS Sierra. This particular server has a 2.6 GHz Intel Core i7, 16 GB RAM and SSD internal drives. The server is mostly idle, and is used as a Time Machine server for 2 users. I have two Drobo Gen 2 external drives attached via daisy-chain Firewire 800 port. The Drobo I tested with has 4 X 7,200 RPM Seagate drives (ST2000DM001). I ran DiskMark from the App Store and the results were consistent with Blackmagic Disk Speed Test: > Sequential Read (MB/s): 10 > > Sequential Write (MB/s): 9.2 > > Random Read (MB/s): 0.3 > > Random Write (MB/s): 1.0 Do these numbers seem low? What steps could I take to improve the drive's IO performance? FYI, the same tool used to measure the performance of the internal SSD drive clocks around 450 MB/s both Read and Write.