I fought with this all weekend.
Server: Rackable Systems C2004, Intel S5000PSL Motherboard, 2 Quad-Core Xeon, 8GB RAM, 2 1TB HDD
I initially had the RAID BIOS (on the motherboard) enabled and the drives in a RAID1 configuration. I am running the Zentyal install from a pen drive.
The installer asks if I want to activate detected RAID and I select "Yes." There is some activity on the drives and a window saying something to the effect of "starting partition manager" shows up for a split second before presenting me with the error message, "No root file system defined." I was never given the option to automatically or manually partition the drives. I tried disabling RAID but that didn't change the results. The installer still asked me about activating the detected RAID system.
Chris