IBM DS8000 manual Extent pool0 Extent pool1, Plan for a reasonable number of extent pools

							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				Processor
Memory						Memory
							Memory
Server0	RIO-G Module				RIO-G Module		Server1
POWER5 2-way SMP
						POWER5 2-way SMP
			DAs
	Rank	1	3	2	4
		5	7	6	8
		9	11	10	12
		Extent pool0		Extent pool1

Figure 12-14 Extent pool affinity to processor complex with pooled ranks in two extent pools

Again what is obvious here is the affinity between all volumes residing in extent pool 0 to the left processor complex, server 0, and vice versa for the volumes residing in extent pool 1 and their affinity to the right processor complex or server 1.

When creating volumes there is no straightforward approach to place certain volumes into certain ranks. For example, when you create the first 20 DB2 logging volumes, they would be allocated in a consecutive fashion in the first rank. The concerned RAID site would then host all these 20 logging volumes. Now with AAL and the high performance and large bandwidth capabilities of the Fibre Channel switched disk storage subsystem, this might not be an issue. You may choose to control the placement of your most performance-critical volumes. This might lead to a compromise between both approaches, as Figure 12-14suggests.

Plan for a reasonable number of extent pools

Figure 12-15presents a grouping of ranks into extent pools which follows a similar pattern and discussion as for grouping volumes or volume pools into SMS storage groups.

276DS8000 Series: Concepts and Architecture