IBM DS8000 manual Performance potential in z/OS environments

		Parellel	z/OS 1.4+
		Sysplex
		FICON		HA
		Director
		RIO-G Module	RIO-G Module
Server 0	L1,2			L1,2	Server 1
Memory	Memory	Processor
			Processor	Memory	Memory
L3	L1,2	RIO-G Interconnect		L1,2	L3
	Memory
Memory		Processor	Processor	Memory	Memory
POWER5 2-way SMP	RIO-G Module		RIO-G Module
					POWER5 2-way SMP

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 12-12shows 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 12-12with 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

270DS8000 Series: Concepts and Architecture