Click to enlarge
In order to fully use the combination of 8 x 4 SATA drives, high-performance architecture is needed. All Broadcom RAIDCore controllers contain a PCI-X interface, which can operate with up to a 133 MHz clock rate. That leads to a maximum bandwidth of 1 GB/s, which today's drives certainly cannot attain. A 60 MB/s per drive bandwidth is realistic. In theory, that adds up to 480 MB/s. But in normal, everyday scenarios, this figure cannot quite be reached (yet).
We used an X5DPE-G2 from Supermicro that was equipped with two PCI-X busses. These busses can each operate two PCI-X cards (66 MHz clock rate), meaning that we could achieve a bandwidth of 4 x 512 MB/s.