Did some testing with the GEN 3 on the MAC, testing the difference between WD Green drives and WD Black drives.
All testing was completed using the following settings:
-15" Macbook PRO Retina display (late 2012)
-2.3 GHz Intel Core i7
-8 GB RAM
-OSX 10.9.3
Testing was performed with the GEN 3 fully populated with either WD green drives or WD black drives. Testing was done following this article: http://support.drobo.com/app/answers/detail/a_id/787/kw/performance%20test
GEN 3 with Green drives installed.
http://www.amazon.com/WD-Green-Desktop-Hard-Drive/dp/B006GDVREI
The Green drives showed an average read time of 81 MB/s, with average writes around 52 MB/s. You do see read peaks as high as 92, and many mid to high 80s, so reads are decent with Green drives. Writes did have some peaks of 65, and remained steady in the high 50s low 60s.
GEN 3 with WD Black drives installed.
The WD Blacks showed a large increase in performance, with reads as high as the 200 MB/s, and Writes as high as 179 MB/s. Largely increased performance with the black drives, with both reads and writes averaging in the triple digits.
Conclusion: If performance is a large need, it can be worthwhile to invest in higher end drives. This includes any NAS quality drive, or even enterprise class SATA drives.
If anyone else has any other performance tests on the MAC with the GEN 3, feel free to share. Please post the make and model of the drives, and a link to the drives you have installed. Please also post some details of the MAC you are using, and please do make sure it is on USB 3.0.