Hmm. I think the headswap to the A700 could have been done differently - by adding the shelf to the existing system and partitioning the disks to add to the existing root aggr+volume before doing it, but I'm not sure exactly what led to the current situation, and I think moving away from it is probably too difficult to consider at this time.
At this point, I think the best action would be to consider adding the SSDs as a seperate RAID group into an existing SSD data aggregate (even if they don't match in size, it would normally be ok) or create a new aggregate with just them in.
You can send me a message with your system serial number and company name if you have autosupport on and would like me to take a more detailed look.
In our case, we added the new 24x890GB SSD for increasing the required root volume size, but didn't partition them as you suggested we should.
As it is now, I am interested in two options that you pointed out, and would like you to weigh in which one I should go for.
1. With total of 18x890GB, creating a new aggr on a node would cause two nodes in HA out of balance, personally, I prabably would not prefer.
2. Adding 9x890GB to each node into the existing aggr as a new rg, AND deducting two disk as parities, that would probably add 6TB more in each aggr, assuming the size mismatching is alright, is it worth doing it?
I am going to send you 2 serial numbers for these two new heads. Due to issues here with sending out on-demand Autosupport, you might not be able to see the updates, but there is a manually trigged one there.