FICON Express2 Channel Performance Version 1.0 - IBM

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FICON Express2 Channel Performance Version 1.0 Page 25 The Generation (G) field tells you a combination of which generation FICON channel is being used and the speed of the fibre channel link for this CHPID at the time the machine was IPL’d. A “4” appears in the G field for CHPID 95 in Figure 22. This means that this channel is a FICON Express2 channel with a link speed of 2 Gbps. If this channel was connected to a 1 Gbps director, then there would be a “3” in the G field. A “2” indicates a FICON Express channel with a link speed of 2 Gbps and a “1” indicates a FICON Express channel operating at 1Gbps. For a given FICON channel there are three possible entries under UTILIZATION (%): 1. PART denotes the FICON processor utilization due to this logical partition. 2. TOTAL denotes the FICON processor utilization for the sum of all the LPARs. 3. BUS denotes the FICON PCI bus utilization for the sum of all the LPARs. The FICON processor is busy for channel program processing, which includes the processing of each individual channel command word (CCW) in the channel program and some setup activity at the beginning of the channel program and cleanup at the end. A very precise algorithm is used for calculating zSeries FICON Express and FICON Express2 channel utilizations. This algorithm is based on monitoring the amount of time the channel processor spends doing various separate functions, and the results of this algorithm give a much more accurate measure of FICON processor busy time than the original algorithm based on counting command and data sequences, which is still used for 9672 G5/G6 FICON channels. The FICON bus is busy for the actual transfer of command and data frames from the FICON channel chip to the fibre channel adapter chip, which is connected via the fibre channel link to the director or control unit. For FICON and FICON Express channels, the FICON bus is also busy when the FICON processor is polling for work to do. This is why one can see anywhere from 5 to 15% FICON bus utilization on the RMF Channel Activity report during time intervals when there are no I/Os active on those channels. The new FICON Express2 channels, however, no longer use the bus for polling and therefore the bus utilization should be less than 1% for these channels when there are no I/O’s active for an entire RMF reporting interval. The actual FC channel processor and bus utilizations as reported by RMF will vary by workload and by channel type. As shown in Figure 22 above, FICON Express2 channels provide bandwidth information (MB/SEC) not available for ESCON channels. This is provided separately for READs and WRITEs since the fibre channel link is full duplex, at both the logical partition level (PART) and the entire system level (TOTAL). Fibre channel link utilizations are not directly reported on RMF but can be easily calculated by dividing the
FICON Express2 Channel Performance Version 1.0 Page 26 READ or WRITE MB/sec by the link capacity. Several examples of FICON Express2 channel processor, bus and link utilizations based on I/O driver benchmark measurements are displayed in Figures 5 through 17 of this paper. With FICON Express2 channels, customers should continue to analyze their I/O activity by looking at the DASD or TAPE activity reports, just as they did with FICON, FICON Express and ESCON channels. An example of a Direct Access Device Activity report is shown in Figure 23. device activity report...response times... benefit of PAVs... D I R E C T A C C E S S D E V I C E A C T z/OS V1R6 SYSTEM ID xxxx DATE 01/24/2005 RPT VERSION V1R5 RMF TIME 11.09.28 DEVICE AVG AVG AVG AVG AVG AVG AVG DEV DEVICE VOLUME PAV LCU ACTIVITY RESP IOSQ CMR DB PEND DISC CONN NUM TYPE SERIAL RATE TIME TIME DLY DLY TIME TIME TIME 4612 33903 DS3B02 1 0037 54.736 2.2 1.2 0.0 0.0 0.2 0.4 0.4 4613 33903 DS3B03 1 0037 48.996 8.7 5.3 0.0 0.0 0.2 1.8 1.4 4616 33903 DS3B06 1 0037 15.196 8.0 2.5 0.0 0.0 0.2 3.1 2.2 4617 33903 DS3B07 1 0037 20.761 9.7 3.6 0.0 0.0 0.2 3.3 2.6 461C 33903 DS3B0C 1 0037 17.189 13.6 6.6 0.0 0.0 0.2 3.8 2.9 461E 33903 DS3B0E 1 0037 41.288 9.0 4.9 0.0 0.0 0.2 2.3 1.7 LCU 0037 1196.01 3.5 1.7 0.0 0.0 0.2 0.9 0.9 4612 33903 DS3B02 4 0037 55.669 0.5 0.0 0.0 0.0 0.2 0.1 0.2 4613 33903 DS3B03 4 0037 50.145 1.8 0.0 0.0 0.0 0.2 0.8 0.8 4616 33903 DS3B06 4 0037 13.828 8.2 0.0 0.0 0.0 0.2 4.3 3.7 4617 33903 DS3B07 4 0037 20.348 6.4 0.0 0.0 0.0 0.2 3.3 2.9 461C 33903 DS3B0C 4 0037 16.929 8.0 0.0 0.0 0.0 0.2 4.2 3.6 461E 33903 DS3B0E 4 0037 41.106 3.4 0.0 0.0 0.0 0.2 1.7 1.5 LCU 0037 1226.54 1.7 0.0 0.0 0.0 0.2 0.7 0.8 Figure 23 Here one can examine the AVG RESP TIME and various response time components (IOSQ, PEND, DISC and CONN times) for activity to the LCUs attached to the FICON Express2 channels. If response time is a problem, then the response time components need to be looked at. If disconnect time is a problem, then an increase in CU cache size might help. If IOSQ time is a problem, then Parallel Access Volumes might help. Figure 23 shows an example of the reduction in IOSQ time experienced on an IMS benchmark measurement when 4 PAVs were defined vs. 1. In this particular case, IOSQ time improved from an average of 1.7ms to 0ms for this LCU. If PEND or CONNECT times are too high, then one
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