For example, at this moment I don't have an information how much bandwidth do you need between main chassis and expansion box.
I know some of the product supports SAS, daisy chaining. faster is better from the view of performance, expand-ability. But what I don't know is if people satisfy that spec, speed and cost or not. In some view, I believe there is a customer want to have cheaper, but slower solution such as USB3.0. I said USB3.0 but it's still have 5.0Gbps band width.
USB3.0 case, I guess issue is "easy to pull the plug". If, that's the only complain for this solution, we may consider the solution with latch or stopper around USB3.0 port. and could provide the cheaper solution. If you use USB3.0 with USB hub, you also eliminate the single failure point of daisy chaining on SAS. This should be come from the difference of topology, star VS daisy chaining.
How about connect via 10GbE iSCSI? this is another solution. but in this case I guess somebody does't like to need to manage another unit. SAS or USB case, you can manage all the storage from single unit. But iSCSI case, need to manage client side and server side.
Or just use DFS like approach? we maybe able to obtain better band width compare to above 2 idea.
If you have Windows Server or Linux box as a server, you can consolidate storage space by storage pool function of them. In this case NAS/iSCSI doesn't need the capability of expansion by itself.
This is a mostly what I'm thinking...