IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

Chapter 2. Hardware configuration planning 47

2.10.3 FICON attachment

FICON channels started in the IBM 9672 G5 and G6 servers with 1 Gbps. Eventually these

channels were enhanced to FICON Express channels in zSeries 800(z800), zSeries 900

(z900) servers and IBM System z9™ 109, with 2 Gbps.

FICON Express 2 channels are a new

generation of FICON channels that offer improved performance capability over previous

generations of FICON Express and FICON channels. They are supported on the

IBM Eserver zSeries 990 (z990), zSeries 890 (z890) and IBM System z9 109. Figure 2-25

shows the performance enhancement of FICON Express 2.

Figure 2-25 Performance Enhancement of FICON Express2

As you can see, the FICON Express2 channel as first introduced on the zSeries z890 and

z990 represents a significant improvement in both 4K I/O per second throughput and

maximum bandwidth capability compared to ESCON and previous FICON offerings.

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. For example, if there are two FICON Express2 channels, just two FICON

Express2 channels have the potential to provide roughly a bandwidth of 2 x 270 MB/s, which

equals 540 MB/second. This is a very conservative number.

I/O rates with 4 KB blocks are about 13000 I/Os per second per FICON Express2 channel,

again a conservative number. For example, two FICON Express2 channels have the potential

of over 26000 I/Os per second with the conservative numbers. These numbers vary

depending on the server type used.

Note: This performance data was measured in a controlled environment running an I/O

driver program. The actual throughput or performance that any user will experience will

vary depending upon considerations such as the amount of multiprogramming in the user’s

job stream, the I/O configuration, the storage configuration, and the workload processed.

M B/sec Thoroughput(full duplex)

Large sequential R/W interm ix

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48 IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

The ESS 800 has an aggregated bandwidth of about 500 MB/s for highly sequential reads

and about 350 MB/s for sequential writes. DS6800 would be able to perform better than the

ESS with four FICON Express2 channels for highly sequential workload. However, for highly

sequential workload (for example 500 MB/s), the bandwidth of 2 FICON Express2 channels is

540 MB/s, as stated above, it is better to prepare 4 FICON Express2 channels.

The DS6800 can achieve higher data rates than an ESS 800 by its bandwidth. The DS6800

can outperform better than ESS 800 for some sequential workload. But, in a z/OS

environment a typical transaction workload might perform on an ESS 800 Turbo II with a large

cache configuration better than with a DS6800.

Figure 2-26 Fibre Channel/FICON host adapters - FICON attachment

FICON connection limits:

򐂰 Addressing limit, 16,384 (maximum of 8192 devices supported within one DS6000).

򐂰 Up to 512 control unit logical paths per port.

򐂰 FICON channels allow multiple concurrent I/O connections.

򐂰 Channel and link bandwidth: 170 MB/s for FICON Express and 270 MB/s for FICON

Express2.

򐂰 FICON path consolidation using switched point-to-point topology.

򐂰 Link distances 10 km without repeaters and 100 km with extenders.

These characteristics allow more powerful and simpler configurations. The DS6000 supports

up to 8 Fibre Channel/FICON host ports, which allows for a maximum of 8 FICON ports per

machine.

Each Fibre Channel/FICON host port provides one port with an LC connector type. The

adapter is a 2 Gbps card and provides a nominal 200 MB/s full-duplex data rate. The adapter

will auto-negotiate between 1 Gbps and 2 Gbps, depending upon the speed of the connection

Note: The Fibre Channel/FICON host port supports both FICON or FCP, but not

simultaneously; the protocol to be used is configurable on an adapter-by-adapter basis.

zSeries

FICON attachment

•Up to 8 FICON ports per DS6800

•One port with an LC connector type

•Long wave or short wave option

•Up to 200 MB/sec full duplex

•Up to 10 km distance with long wave and

300m short wave

•Each FICON port can address all 32 DS6000

LCU images

Logical paths

•1024 LCU logical paths per FICON port

Addresses

•16,384 device addresses per channel

FICON distances

•10 km distance (without repeaters)

•100 km distance (with extenders)