FICON Express2 Channel Performance Version 1.0 - IBM

FICON Express2 Channel Performance Version 1.0
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Recommended configuration for
determining max capability of a CU port for
benchmark testing
multiple FICON
channels
connected through
a FICON director to
a single CU port
Figure 4
The four basic DASD I/O driver benchmark programs used to evaluate the capabilities of the
new FICON Express2 channels are as follows:
1. 4K bytes per I/O: this channel program processes small blocks of I/O and is capable of
achieving high I/O per second rates but much lower MB/sec rates than large block
channel programs. With the appropriate read/write ratios and CU cache hit ratios, this
benchmark is representative of online transaction processing workloads.
2. 6x27K bytes per I/O: this channel program processes 6 large blocks with 27K bytes each
or 6 half-tracks of data and is capable of achieving high MB/sec but much lower I/O per
second than the small block channel programs. It is representative of the type of channel
programs used in disk to tape backup jobs or other highly sequential batch jobs.
3. 27K bytes per I/O: this channel program processes a single half track of data and achieves
both I/O per second and MB/sec that are in between the extremes of the 4K and 6x27K
bytes per I/O benchmarks.
4. 32x4K bytes per I/O: this channel program processes 32 small (4K byte) blocks of I/O and
is representative of some DB2 pre-fetching utilities and other channel programs that
process long chains of short blocks of data.
Figure 5 below shows the average of all of the LCU (Logical Control Unit) response times for
the 4k read hit benchmark measurement plotted with FICON Processor Utilization(FPU) %s .
Response times in milliseconds are on the left y-axis. FPU %s are on the 2nd or right y-axis.
The knee of the response time curve occurs around 10,000 I/O’s per second and just above
70% FICON Processor utilization (FPU) when running this very simple 4K read hit
benchmark workload. But most real production workloads are more complex than this
z990
FICON
Express2
Channels
W1,X2,Y3,Z4
Director
CU box