IBM DS8000 manual Configuring multipath, Figure B-22 Single points of failure

1. IO Frame
2. BUS
3. IOP	6.	Port
4. IOA
5. Cable	7.	Switch
	8.	Port
	9. ISL

10.Port

11.Switch

12.Port

13. Cable

14. Host Adapter

15. IO Drawer

Figure B-22 Single points of failure

When implementing multipath, you should provide as much redundancy as possible. As a minimum, multipath requires two IOAs connecting the same logical volumes. Ideally, these should be on different buses and in different I/O racks in the iSeries. If a SAN is included, separate switches should also be used for each path. You should also use Host Adapters in different I/O drawer pairs in the DS8000. Figure B-23 on page 387 shows this.

Figure B-23 Multipath removes single points of failure

Unlike other systems, which may only support two paths (dual-path), OS/400 V5R3 supports up to eight paths to the same logical volumes. As a minimum, you should use two, although some small performance benefits may be experienced with more. However, since OS/400 multipath spreads I/O across all available paths in a round-robinmanner, there is no load balancing, only load sharing.

Configuring multipath

iSeries has two I/O adapters that support DS8000:

￿2766 2 Gigabit Fibre Channel Disk Controller PCI

Appendix B. Using DS8000 with iSeries 387