11.5.1 Connect to zSeries hosts

Figure 11-11displays a configuration fragment on how to connect a DS6800 to a FICON host.

blue I/O

preferred path

preferred path

red I/O

blue I/O

red I/O

Server 0

blue

Server enclosure

Server 1

red

Fibre Channel switch

ooo

16 DDM

Fibre Channel switch

Fibre Channel switch

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16 DDM

Fibre Channel switch

Expansion enclosure

Figure 11-11 DS6800 front end connectivity example - partial view

The physical connectivity does not reveal what is important to consider when creating logical volumes and assigning these volumes to LCUs. Before considering different configuration approaches, we provide some general discussion on the potential of the DS6000 series in the following sections.

11.5.2 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 DS6000 series provides only 2 Gbps FCP ports, which can be configured either as FICON to connect to zSeries servers or as FCP ports to connect to Fibre Channel-attached open systems hosts. The example in Figure 11-11shows only two FICON Express channels. But just two FICON Express channels have the potential to provide roughly a bandwidth of 2 x 175 MB/sec, which equals 350 MB/sec. This is a very conservative number. Some measurements show up to 206 MB/sec per 2 Gbps FICON Express channel and 406 MB/sec aggregated for this particular example with just two 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 11-11with only two FICON Express channels has the potential of over

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IBM DS6000 Series manual Connect to zSeries hosts, Performance potential in z/OS environments