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

Page 409
Image 409
IBM DS8000 manual Configuring multipath, Figure B-22 Single points of failure