I little of both depending on the end use. Most of the times we use 3 PCIe raid controllers. Some cases 1 24 port controller works great. Also, we keep at

I little of both depending on the end use. Most of the times we use 3 PCIe raid controllers. Some cases 1 24 port controller works great. Also, we keep at least 2 or 3 in the hot swap mode for reliability.