Hi Jedd,
Congratulations on your new purchase, I'm envious... a new 6200 isn't in the cards for a while for us .
1. If you were using iSCSI, and wanted totally seperate physical networks for multipathing then yes, you could split them into two vif's using 1gb as failover. For NFS, I personally wouldn't (and we don't). You have to consider what would happen in the event of a failure where some system or set of systems is point to a vif with 1x 10g and 1gb for failover. You'd be effectively reducing your available bandwidth by 90%. There is the possibility that this could cause serious contention for that 1gb port, possibly to the point of almost making it unusable. If you have a vif with both 10g's active using IP balancing then you effectively get the redundancy of 2 ports, plug ~20gbit of available bandwidth sans overhead and imbalance. Worst case in the event of a port failure you'd have 50% the bandwidth (but in reality you're not going to be able to push 10 as you're limiting it to 4).
2. Is this a waste of pipe? Is this all thats pointing at the system? Yes and no. Its really a personal call. You have to be able to plan on expanding that 4gb later and having more bandwidth available now means less chance of downtime to reconfigure vifs or add cards in when you expand.
3. Aliasing... we tried this when we had all 1gig and no plans of 10gig. Yes, it does work to get you some additional bandwidth by using additional links (either on separate vifs or on multiple links inside a vif). But we ultimately found it to be more of a headache than it was realy worth with managing the different names, IPs, vifs, etc etc. Now with a 2 port 10gig vif, we have nothing to worry about, we just point everything at the 1 IP address and away it goes.
4. How much time,effort and money do you want to expend, lol? 2x 10g ports in a single vif buys you at worst ( in failover) 10g of bandwidth. All you're allocating is 4g for your storage traffic, shouldn't ever be a problem. Now, if you're worried about the switch that connects to this vifs failing, then yes, you would need two vifs, each plugged in to seperate switch (possibly all the way back to the blades) and with NFS you'd have to use aliasing.
Also, bear in mind that in the event of a total vif failure (for whatever reason) you can always fail over to the other filer.
If I wasn't clear on anything, please let me know.
Best Regards,
Adam S.