IBM DS8000 - Manual (Page 409)

Appendix B. Using DS8000 with iSeries 387
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-robin manner, 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
6. Port
7. Switch
8. Port
1. IO Frame
2. BUS
3. IOP
4. IOA
5. Cable
9. ISL
13. Cable
10. Port
11. Switch
12. Port
14. Host Adapter
15. IO Drawer