Shared Ethernet Adapter: Load Sharing or Virtual Switches?
AnthonyEnglish 270000RKFN Visits (11566)
For network redundancy, you can set up two Shared Ethernet Adapters (SEAs) - one on each Virtual I/O Server (VIOS). The two SEAs work together with one active, the other idle, so the configuration is called failover mode. This is done by a control channel - a heartbeat that works through a virtual ethernet adapter on each SEA. The failover mode is very effective, because it allows you to shut down a single VIOS and automatically have the other SEA on the alternate VIOS take the traffic. With failover mode you can use VLAN tagging, something not available on the Network Interface Backup configuration.
The failover does have one big drawback. The non-active adapter sits idle while all the traffic passes through the primary adapter. With a relatively expensive 10-GB adapter sitting idle, it seems a bit of a waste.
There is a higher availability alternative to this, as explained in the document Using Virtual Switches in PowerVM to Drive Maximum Value of 10Gb Ethernet. If you don't have time to read the whole document, have a look at Rob McNelly's summary in this AIXChange blog post in September.
The Virtual Switch solution required a Network Interface Backup (NIB) configuration on the VIO clients. This would require a primary and a backup virtual Ethernet adapter on each logical partition. This solution was inventive, but I wondered at the time whether it might get a little too complex, especially when you get to a larger number of logical partitions.
Now there is an option for configuring SEA failover (not Netwrok Interface Backup) with Load sharing mode. This means you can have both physical network adapters active, instead of one sitting idle in the marketplace, waiting to be called up for duty. This loadsharing configuration leaves any complexity on the VIOS and away from the VIO clients. You have to be running VIOS version 220.127.116.11 or later (check your version by logging in as padmin and running the ioslevel command).This saves the manual load balancing by hand which happens when you use NIB. The load sharing option looks to me to be a much more attractive option than the earlier solutions.
It's quite easy to configure SEA failover with load sharing.
For more on Virtual I/O Server Load sharing (as well as some excellent slides on the Shared Storage Pools), see here.