The XIV consists of a number of modules (from 6 to 15), of which a subset are Interface Modules (meaning they have fibre channel and iSCSI interfaces)
Zone the SAN so that each HBA in an LPAR has 3 paths to the XIV.
If an LPAR has two HBAs, then zone the first HBA to modules 4, 6 and 8 and the second HBA to modules 5, 7 and 9.
For the next LPAR, do the reverse and zone the first HBA to modules 5, 7 and 9 and the second HBA to modules 4, 6 and 8.
If we look at a typical dual fabric 15 module XIV, it would be cabled as pictured below.
Port 1 on each XIV module attaches to Fabric 1
Port 3 on each XIV module attaches to Fabric 2.
Ports 2 and 4 are reserved for replication and mirroring.
But look closely at the use of colours in this lovely Visio diagram I created.
Host 1 is zoned using the links in blue.
Host 2 is zoned using the links in red.
Notice how they round robin between the odd and even numbered interface modules.
Rules of thumb
- The maximum number of paths you can zone to an AIX LPAR is 32. There is no real benefit in going beyond 24 paths.
- For a full XIV, zone half the interface modules to one HBA and half the interface modules to the other HBA.
- If an LPAR has only one HBA, then zone it to three modules. Only zone it to six modules if the LPAR has very high throughput requirements.
- If you want 12 or more paths, use four HBAs.
- If you have less than 6 interface modules (because you have a partially populated XIV) then zone each HBA to each module until each HBA is zoned to at least 3 modules.
- Use single initiator zones. This means each zone contains one host port and between three and six XIV ports.
- Don't mix tape and disk on the same HBA. Use separate HBAs for tape traffic.
Because there is some evidence that having excessive paths can slightly raise CPU utilisation.
The other reality is that having multiple duplicate paths won't make your system more reliable.