Intel 170 Servers manual Disk I/O Throughput, ISCSI Target, IXA Capacity Comparison MB per Second

yA storage space which is linked as shared, or a disk with caching disabled, requires more CPU to process write operations (approx. 45%).

ySequential operations cost approximately 10% less than the random I/O results shown above.

yEven though a Windows disk driver may have write cache enabled, some Windows applications may request to bypass the cache for some operations (extended writes), and these operations would incur the higher CPW cost.

yIf your application load is skewed to the upper or lower average disk operations, you may encounter a smaller or larger CPW cost than indicated by the “rules of thumb”.

17.5 Disk I/O Throughput

The chart below compares the throughput performance characteristics of the current IXA product against the new iSCSI solution. The charts indicates an approximate capacity of a single target HBA when running various sizes and types of random operations.

The chart below also demonstrates that the new page based architecture utilized in the iSCSI solution provides better over all performance in Write and Read scenarios. While the sector based architecture of the current IXA provides slightly better performance in small block Write operations, that difference is quickly reversed when block sizes reach 4k. 4k block sizes and higher are representative of more I/O server scenarios.

As with all performance analysis, the actual values that you will achieve are dependent on a number of variables including workload, network traffic, etc..

iSCSI Target, IXA Capacity Comparison

MB per Second

160

140

120

MB/sec

100

80

60

40

20

0

1k RandWrite

2k RandWrite

4k RandWrite

8k RandWrite

16k RandWrite

24k RandWrite 32k RandWrite

64k RandWrite

128k RandWrite

512 RandRead

1k RandRead

2k RandRead

4k RandRead

8k RandRead

16k RandRead

24k RandRead

32k RandRead 64k RandRead 128k RandRead

512 RandRW 1k RandRW 2k RandRW 4k RandRW

8k RandRW

16k RandRW

24k RandRW

32k RandRW

64k RandRW

128k RandRW

512 RandWrite

IXA

iSCSI 1 Targ 1 Init Std

iSCSI 1 Targ 4 Init Std iSCSI 1 Targ 4 Init Jumbo

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
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