I have a Drobo-S, hooked up via SATA with a Tempo SATA E2P (TSATAII-E2P) card. MacPro 2.8 gHz 8 core, 2008 tower. 10gb Ram, OS 10.6.6
4 out of 5 drive bays in use, single drive protection is on.
The Drobo is constantly indexing. On for ~15 secs, then off for 10~15 sec, then on again.
Drobo tech...