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270 DS8000 Series: Concepts and Architecture
Figure 12-12 DS8100 frontend connectivity example - partial view
Note that this figure only indicates the connectivity to the Fibre Channel switched disk
subsystem through its I/O enclosure, symbolized by the rectangles.
Each I/O enclosure can hold up to four HAs. The example in Figure 12-12 shows only eight
FICON channels connected to the first two I/O enclosures. Not shown is a second FICON
director, which connects in the same fashion to the remaining two I/O enclosures to provide a
total of 16 FICON channels in this particular example. The DS8100 disk storage server
provides up to 64 FICON channel ports. Again note the very efficient FICON implementation
in DS8000 FICON ports.
12.5.2 Performance potential in z/OS environments
FICON channels started in the IBM 9672 G5 and G6 servers with 1 Gbps. Eventually these
channels were enhanced to FICON Express channels in IBM 2064 and 2066 servers, with
double the speed, so they now operate at 2 Gbps.
The example in Figure 12-12 with 16 FICON Express channels has roughly the potential to
provide a bandwidth of 16 x 175 MB/sec, equal to about 2.8 GB/sec. This is a very
conservative number. Some measurements show up to 206 MB/sec per 2 Gbps FICON
Express channel and 3.3 GB/sec aggregated for this particular example with 16 FICON
Express channels.
I/O rates with 4 KB blocks are in the range of 6,800 I/Os per second or more per FICON
Express channel, again a conservative number. A single FICON Express channel can
actually perform up to about 9,000 read hit I/Os per second on the DS8000. This particular
example in Figure 12-12, with 16 FICON Express channels, has the potential of over 100,000
I/Os per second. These numbers are rough considerations and rely on 100% read hit rates for
RIO-G ModuleRIO-G Module
z/OS 1.4+
HA
RIO-G Interconnect
FICON
Director
Parellel
Sysplex
RIO-G Module
POWER5 2-way SMP
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POWER5 2-way SMP
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RIO-G Module
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