Logical partition concept: Bus

 

A bus is a conductor that is used for transmitting signals or power.

A system I/O bus conducts instructions from memory to the devices that are attached to the input/output processors (IOPs). A system I/O bus also conducts instructions from the IOPs back to memory.

The main system unit contains one system I/O bus. The primary partition always uses bus 1. Secondary partitions can share this bus. Most expansion units contain at least one bus as well.

Every logical partition needs a bus which the logical partition can either own dedicated or shared with other logical partitions. Each logical partition can use (without owning) a system I/O bus. You can dynamically change which logical partition owns the bus or the type of bus ownership (shared or dedicated) provided the owning partition owns the bus shared.

It is possible to divide up your resources by system I/O bus when you create your logical partitions. This is called bus-level I/O partitioning. In this situation, you assign all resources (IOPs, IOAs, and devices) that are attached to the bus to only one logical partition.

It is also possible to share a bus and divide up the resources on the bus according to IOPs. This is called IOP-level I/O partitioning. In this situation, you assign all resources (IOAs and devices) that are attached to a single IOP to only one logical partition at a time. You may assign other IOPs attached to this same bus to any other (or to the same) logical partition.

When you add a bus to a logical partition, select whether to share the bus with other logical partitions. You have the following options for bus ownership type:

• Own dedicated: you assign all IOPs, resources, and empty card positions to the partition (bus-level I/O partitioning).

• Own bus shared: Some IOPs along with their empty card positions can be assigned go with the bus owner (IOP-level I/O partitioning).

• Use bus shared: Another logical partition lists the bus as own bus shared, but this logical partition also uses the bus. In this situation, the owning logical partition may experience slightly improved performance. Consider having the partition using high data transfer rate resources to own the bus.

You must assign the own dedicated type to any bus that contains the OptiConnect hardware.

From the Configure Logical partition window, you can view all of the buses on the system. You may perform concurrent maintenance from the owning logical partition (dedicated buses only) or from the primary partition. However, perform concurrent maintenance for shared buses from the primary partition.

 

Parent topic:

Hardware for logical partitions

Related concepts
Logical partition concept: Memory Logical partition concept: IOP Logical partition concept: Expansion unit Logical partition concept: Bus-level and IOP-level I/O partitions Dynamically switching IOPs between partitions Communication options for logical partitions