I/O: Concepts

System, Cells, SBA, LBA, Devices and Relationships

On a server, an I/O device communicates to the system through the LBA and SBA. The path looks like Figure 8-1.

Figure 8-1 System to I/O Device Relationship

This corresponds to the ioscan hardware path output for an I/O device of sba/lba/ ... /device.

A LBA actually owns all the devices attached to it. In the example below, all the I/O devices attached to LBA 0 are owned by LBA 0, and the hardware paths of those I/O devices begin with 0/0 (sba/lba). (Cells are discussed later and would change the hardware path to cell_ID/sba/lba.)

Figure 8-2 LBA Owns Multiple I/O Devices

It is at the LBA level where vPars assigns I/O. In the example below, this means that LBA 0 can be assigned to at most one virtual partition. If LBA 0 is assigned to vparN, it is implied that all I/O devices attached to LBA 0 are assigned to vparN.

Figure 8-3 vPars Allocates I/O at the LBA Level

A SBA has multiple LBAs attached to it; it is a hierarchical relationship. Nevertheless, assignments in vPars remain at the LBA level, and each LBA can be assigned to a different virtual partition.

	NOTE: Regarding syntax and how vPars commands interpret what is specified on the command line, see “I/O: Allocation Notes”. Even if there are shortcuts in assigning LBAs, vPars assigns per LBA.

In the example below, each LBA (shown in brackets) can be assigned to a different virtual partition.

Figure 8-4 vPars Allocates at LBA Level not SBA Level

A system has multiple SBAs, but assignments remain at the LBA levels.

Figure 8-5 vPars Allocates at LBA Level not SBA Level

With the addition of cells (an nPartitionable server), there are more SBAs, but I/O assignments remain at the LBA level:

Figure 8-6 vPars Allocates at LBA Level not Cell Level