FCP statistics (SLES9 / SLES10)

Test environment

For both SCSI and ECKD devices, there are possibilities included in Linux on System z to collect various statistical data such as I/O request data sizes or I/O latencies.

This study mainly is aimed at investigating FCP statistics, the performance aspect of collecting statistical data, and the comparison of SCSI to ECKD. For an analysis of ECKD statistics, see DASD statistics.

As a basis for our measurements we chose the distribution SLES10 SP1 as being a recent distribution containing the complete set of SCSI and ECKD statistics.

The measurements were conducted with a SLES10 SP1 (kernel level 2.6.16.46-0.4-default) on a System z9 with a DS8000 storage server. The load used to generate I/O was the IOzone benchmark.

In our measurements, the IOzone benchmark generated I/O load for 1, 2, 4, 8, 16, 32, or 64 disks in 3 consecutive iterations using a file size of 700 MB. Furthermore, different write and read modes were processed: Sequential Write, Sequential Read and Random Write/Read. Data were collected for all these cases, but in detail we examined the one and the 16 disk case.

Since the collected data are displayed separately for each single disk, we combined the values from 16 disks to make them comparable to the ECKD values.

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