Once you start thinking about redundancy, your pulse beats fast every time you have a whiff of what might be a Single Point of Failure. When that happens to you, then deep in your heart you know you have a mission in life. IBM Power Virtualisation will help you with that mission, because it allows you to set up a really robust network configuration from the Power Systems end.
Between the SEAs
With a dual-VIO server configuration (only available on the HMC, not IVM), you can set up a Shared Ethernet Adapter (SEA) in failover mode, which provides redundancy for the network. This really involves two SEAs - one on each VIO server. They communicate by means of a virtual adapter on each VIOS which is known as the control channel adapter. The control channel works as a heartbeat using its own VLAN, so that if the SEA with the higher priority (say priority 1 on VIO Server 1) loses its link to the world, the lower priority adapter (say priority 2 on VIOS 2) takes over.
Grow a trunk
You can grow your bandwidth and multiply redundancy by creating a SEA on a link aggregation / etherchannel / trunk (pick your terminology). You may have a 2-port adapter in an etherchannel on one VIOS server and another 2-porter on the other. Each SEA can use an etherchannel as its "real" adapter. But why stop there? After all, things can go wrong.
A shocking story (not for the faint hearted)
You just never know when you're going to need just a little bit of extra bandwidth, and there's one other thing to consider. Just in case your nightmares are running a little short in the things-I-should-be-worried-about department, back in 1995 I heard of a network adapter on a legacy dev machine which was dropping occasional packets and needed to be replaced.
If you've still got a pulse, I'm sure you'll agree
That's really SCARY!
So, what are you going to do about it?
Here's what: add more adapters and ports to your etherchannel. (You may now exhale)
See this updated post: Opening the Trunk Under the SEA
So how do you do it without an outage?
Let's say you have SEA 1 (priority 1) on VIOS 1 and SEA 2 on VIOS2. Here are the steps:
- On VIOS1 confirm SEA1 is in Active mode
entstat -all entN | grep Active
- Turn off the failover mode on SEA2 (log onto VIOS2)
chdev -dev entN -attr ha_mode=disabled
- On VIOS1, confirm traffic is going through SEA1 (repeat step 1 above)
- On VIOS2, remove the SEA2
rmdev -dev entN (and enN and etN)
- cable additional ports for SEA2 and configure those switch ports as part of the trunk
- On HMC, assign additional adapter to VIOS2 DLPAR / Add to VIOS2 partition profile (if required)
- add your ports to your etherchannel on VIOS2 using VIOS command cfglnagg
cfglnagg -add etherchannel new_adapter
- Create SEA on VIO2 with failover as per documentation using
mkvdev -sea ...
Be sure to include the high availability mode and the control channel adapter:
-attr ha_mode=auto ctl_chan=entsomething
- On VIOS1 run
chdev -dev entN -attr ha_mode=standby
- On VIOS2, confirm traffic is going through SEA2
entstat -all entN | grep Active
- On VIOS1 repeat steps 2 to 8 above
Sleeping in peace, under the SEA
After that, you can sleep in peace, because everything's under control, under the SEA.