IBM DS8000 manual Minimize the number of extent pools, 275

								HA
			RIO-G Module		RIO-G Module
		L1,2					L1,2
Memory		Memory	Processor					Memory
						Processor	Memory
	L3	L1,2	Processor				L1,2	L3
		Memory
Memory						Processor	Memory
								Memory
Server0		RIO-G Module				RIO-G Module		Server1
POWER5 2-way SMP								POWER5 2-way SMP
Rank				DAs
	Extent pool0		Extent pool2	Extent pool4	Extent pool1	Extent pool3	Extent pool5
		1	3	5	2	4		6
		7	9	11	8	10		12
	Extent pool6		Extent pool8	Extent pool10	Extent pool7	Extent pool9	Extent pool11

Figure 12-13 Extent pool affinity to processor complex with one extent pool for each rank

Figure 12-12also indicates that there is no affinity nor a certain preference between HA and processor complexes or servers in the DS8000. In this example either one of the two HAs can address any volume in any of the ranks, which range here from rank number 1 to 12. Note there is an affinity of DAs to the processor complex. As Figure 12-3 on page 259 depicts, a DA pair connects to two switches respectively to two pairs of switches. The first DA of this DA pair connects to the left processor complex or server 0. The second DA of this DA pair connects to the other processor complex or server 1.

Minimize the number of extent pools

The other extreme is to create just two extent pools when the DS8000 is configured as CKD storage only. You would then subdivide the disk subsystem evenly between both processor complexes or servers as Figure 12-13shows.

Chapter 12. Performance considerations 275