FICON Express2 Channel Performance Version 1.0 - IBM

FICON Express2 Channel Performance Version 1.0
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connected to the same ESTI-M card and these would share a single 2GB/sec ESTI link from
the ESTI-M card to the MBA chip.
The third row depicts the path followed by commands and data frames transferred from a
FICON channel to a FICON CU port. Each of the 4 FICON Express2 channels on the FICON
Express2 channel card has its own PCI bus connected to an industry standard Emulex fibre
channel adapter chip which handles the transmitting and receiving of frames across the
2Gbps FC (fibre channel) link. The FC link could be connected point-to-point to a CU port
or through a source and destination Fabric port (f-port) on a director. Both the channel and
the CU ports are called N-ports in the Fabric. If two directors were cascaded together the
ports connecting the two directors would be called E-ports and the link connecting the two
directors is an ISL or inter-switch link. One source of confusion that I have seen very often is
to use the term channel adapter or even just channel for the CU port. In this paper, when I
use the term channel, I mean the chip on the card that is plugged into the zSeries CEC. It is
important to understand that FICON channels and FICON CU ports can have very different
performance capabilities. It is the performance capabilities of FICON Express2 channels that
are presented in this paper.
In general, each of the various resources depicted above are utilized at different levels
depending on the type of I/O that is being processed and the numbers of each resource (CPs,
SAPs, MBA chips, ESTI-M cards, channel cards, director ports and CU ports) that are in the
configuration. For the most part, with small block I/O operations, processors such as the
FICON channel and the CU port are pushed to higher levels of utilization than the buses and
links. In contrast, I/O’s that transfer a lot of data push the buses and links to higher levels of
utilizations than the processors. The resource that gets pushed to the highest utilization will
be the one that limits higher levels of throughput from being achieved.
FICON Express2 benchmark measurement results
To achieve maximum channel capabilities, I/O driver benchmark measurements were
conducted using a configuration with 4 FICON Express2 channels on 4 different channel
cards connected through three 2Gbps directors to 4 ports on each of 6 different control unit
(CU) or storage subsystem boxes as depicted in Figure 3: