IBM DS8000 manual 277, Mix of extent pools

			blue I/O	red I/O		blue I/O	red I/O
		blue server						red server
		Server0			DAs			Server1
		POWER5 2-way						POWER5 2-way
								SMP
		SMP
Rank		SGLOG1						SGLOG2
	Extent pool0		Extent pool2			Extent pool3		Extent pool1
		1	3	5		5	3	1
			7	9	SGPRIM	9	7
SGHPC1		11						11	SGHPC2
	Extent pool4			blue pool		red pool		Extent pool5

Figure 12-15 Mix of extent pools

Create two general extent pools for all the average workload and the majority of the volumes and subdivide these pools evenly between both processor complexes or servers. These pools contain the majority of the installed ranks in the DS8000. Then you might consider two or four smaller extent pools with dedicated ranks for high performance workloads and their respective volumes. You may consider defining storage groups accordingly which are congruent to the smaller extent pools.

Consider grouping the two larger extent pools into a single SMS storage group. SMS will eventually spread the workload evenly across both extent pools. This allows a system-managed approach to place data sets automatically in the right extent pools. With more than one DS8000 you might consider configuring each DS8000 in a uniform fashion. We recommend grouping all volumes from all the large extent pools into one large SMS storage group, SGPRIM. Cover the smaller, high performance extent pools through discrete SMS storage groups for each DS8000. With two of the configurations displayed in

Figure 12-15,this ends up with one storage group, SGPRIM, and six smaller storage groups. SGLOG1 contains Extent pool0 in the first DS8100 and the same extent pool in the second DS8100. Similar considerations are true for SGLOG2. For example, in a dual logging database environment this allows you to assign SGLOG1 to the first logging volume and SGLOG2 for the second logging volume. For very demanding I/O rates and to satisfy a small set of volumes, you might consider keeping Extent pool 4 and Extent pool 5 in both DS8100s separate, through four distinct storage groups, SGHPC1-4.

Figure 12-14shows, again, that there is no affinity between HA and processor complex or server. Each I/O enclosure connects to either processor complex. But there is an affinity between extent pool and processor complex and, therefore, an affinity between volumes and processor complex. This requires some attention, as outlined previously, when you define your volumes.

Chapter 12. Performance considerations 277