In transparent failover, units D00 through D99 are accessed through port 1 of both controllers. Units D100 through D199 are accessed through port 2 of both HSG80 controllers (with the limit of a total of 128 storage units).
You cannot achieve a
You can, however, add the hardware for a second bus (another KGPSA, switch, and RA8000/ESA12000 with associated cabling) and use LSM to mirror across the buses. However, because you cannot use LSM to mirror the cluster root (/) file system, member boot partitions, the quorum disk, or swap partitions you cannot obtain an NSPOF transparent failover configuration, even though you have increased availability.
6.3.2Fibre Channel Cluster Configurations for
With
•The host controls the failover by accessing units over a different path or causing the access to the unit to be through the other HSG80 controller (one controller does not fail over to the other controller of its own accord).
•Each cluster member system has two or more KGPSA host bus adapters (multiple paths to the storage units).
•Normally, all available units (D0 through D199, with a limit of 128 storage units) are available at all host ports. Only one HSG80 controller will be actively doing I/O for any particular storage unit.
However, both controllers can be forced active by preferring units to one controller or the other (SET unit PREFERRED_PATH=THIS). By balancing the preferred units, you can obtain the best I/O performance using two controllers.
_____________________ Note _____________________
If you have preferred units, and the HSG80 controllers restart because of an error condition or power failure, and one controller restarts before the other controller, the HSG80 controller restarting first will take all the units, whether they are preferred or not. When the other HSG80 controller starts, it will not have access to the preferred units, and will be inactive.
