Compaq ProLiant 1000 I/O Performance Tuning of Compaq Servers - Page 7

I/O Performance Tuning of Compaq Servers 7 the bridge chip itself, but also from any synchronization or contention with the primary bus. Simply stated, I/O loads on the secondary bus are not handled as efficiently as equivalent loads on the primary bus. When placing devices on the secondary bus, select the adapters with the lightest I/O load. Microprocessor Motherboard Chipset System Memory 133MB/s Primary PCI Bus 133MB/s PCI Bridge Chip Se1c3o3nMdBar/y PCI Bus s PCI Slot PCI Slot PCI Slot PCI Slot PCI Slot PCI Slot PCI Slot PCI Slot Figure 2. Bridged PCI Architecture Peer PCI bus P In Peer PCI busses, however, you should attempt to balance the I/O load between the busses. Since each 32-bit PCI bus can move 133 MB of data per second, making efficient use of both PCI busses can deliver 266 MB/s of combined throughput. By balancing the I/O load evenly between peered PCI busses, you ensure most efficient use of PCI throughput. Although evenly distributing adapters between the two busses is a good starting point, balancing the load on the two PCI busses requires a bit more insight into the loads generated by each type of device. Generally, the guidelines below will deliver a balanced bus when adding controllers to your server. 1. When installing an even multiple of network or array controllers, split the controllers evenly between the busses. For example, if you were adding two array controllers and two network controllers, you should put one each of the network and array controllers in each of the PCI busses. 2. If installing an "odd" number of controllers, for example, two NICs (Network Interface Controller) and one drive array controller, split the two network controllers between the busses. Network controllers consume more bandwidth than array controllers do, so it is best to split the workload between two busses if possible. ECG044.0399