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Chapter 12. Performance considerations 277
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 12-14 shows, 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.
Rank
DAs
Extent pool5
Extent pool1
Extent pool3
Extent pool4
Extent pool2
Extent pool0
1
3
5
7
9
11
1
3
5
7
9
11
POWER5 2-way
SMP
Server0
POWER5 2-way
SMP
Server1
red I/O
blue pool
red pool
blue I/O
red I/Oblue I/O
blue server
red server
SGLOG2
SGPRIM
SGHPC2
SGLOG1
SGHPC1