A configurable rack server backplane that provides either two-lane or four-lane PCIe bus connections at each the individual drive bays supported by the backplane. The backplane may be configured to provide each drive bay with a two-lane PCIe connection or a four-lane PCIe connection based on the selection of cable connectors that are provided by the backplane. The backplane may be re-configured to distribute the bandwidth of a sixteen-lane PCIe bus connection among four drive bays, each using four-lane PCIe links or among eight drive bays, each using two-lane PCIe links. The backplane may additionally support tiered distribution of the PCIe bus connection bandwidth, such as two-lane PCIe links for certain drive bays and four-lane PCIe links for other drive bays. Each two-lane and four-lane PCIe link provided by the backplane is comprised of consecutively numbered PCIe lanes of the PCIe bus connection.