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264 DS8000 Series: Concepts and Architecture
switch has two ports to connect to the next switch pair with 16 DDMs when vertically growing
within a DS8000. As outlined before, this dual two logical loop approach allows for multiple
concurrent I/O operations to individual DDMs or sets of DDMs and minimizes arbitration
through the DDM/switch port mini loop communication.
12.3.5 Vertical growth and scalability
Figure 12-9 shows a simplified view of the basic DS8000 structure and how it accounts for
scalability.
Figure 12-9 DS8100 to DS8300 - scale performance linearly - view without disk subsystems
Although Figure 12-9 does not display the back-end part, it can be derived from the number
of I/O enclosures, which suggests that the disk subsystem also doubles, as does everything
else, when switching from a DS8100 to an DS8300. Doubling the number of processors and
I/O enclosures accounts also for doubling the performance or even more.
Again note here that a virtualization layer on top of this physical layout contributes to
additional performance potential.
12.4 Performance and sizing considerations for open systems
To determine the most optimal DS8000 layout, the I/O performance requirements of the
different servers and applications should be defined up front since they will play a large part in
dictating both the physical and logical configuration of the disk subsystem. Prior to designing
the disk subsystem, the disk space requirements of the application should be well
understood.
RIO-2 Interconnect
RIO-2 Interconnect
RIO-2 Interconnect
I/O enclosure
I/O enclosure
I/O enclosure
I/O enclosure
Dual two-way processor complex
Dual four-way processor complex
Fibre Channel switched disk subsystems are not shown
RIO-G Module
POWER5 4-way SMP
RIO-G Module
Memory
L3
L3
Memory
Memory
Processor
Processor
L1,2
Memory
L1,2
Memory
Memory
L3
L3
Memory
Memory
Processor
Processor
L1,2
Memory
L1,2
Memory
Server 1
RIO-G Module
POWER5 4-way SMP
RIO-G Module
Memory
L3
Memory
Processor
Processor
L1,2
Memory
L1,2
Memory
Memory
L3
Memory
Processor
Processor
L1,2
Memory
L1,2
Memory
Server 0
RIO-G Module
POWER5 2-way SMP
Memory
L3
L3
Memory
Memory
Processor
Processor
L1,2
Memory
L1,2
Memory
Server 1
RIO-G Module
POWER5 2-way SMP
Memory
L3
Memory
Processor
Processor
L1,2
Memory
L1,2
Memory
Server 0