We don't recommend having any other firewire devices,especially   drives,connected to the same bus as the Fireface.Instead,t youshould consider adding a firewire controller card in order to get a separate,dedicated bus for other firewire devices single Fireface,a firewire 400 bus is sufficient.For best results,
I  
would look for a controller with a Texas Intsruments chip.
Recently,RME has issued separate firmware revisions for the Fireface;  one for units with the TCO(Time code Option),and one for units without the TCO.The separate firmware revs,and a new driver,have  
resolved the issues that some users were experiencing.
Finally,unless the user is working with very high sample rates,I  
would reconsider using a SATA Raid.Ordinary 8-meg cache IDE drives can play 70+ tracks of 44.1 audio without putting an additional load on the PCI bus.