I know I need to ask our sales rep. but, I just wanted to get an rough idea, and then take a step further.
We need to dump about 10TB backup data to the storage, It'd be cheap if we use SATA drive(maybe 1TB drive?), but currently we only have SAS (600GB each). so, I am thinking how much difference between these two shelves, then make the decision from there.
Flashcache will improve your read performance greatly, I see up to 13000 iops from my sata stack.
You just need free sas ports to dedicate to the sata stack. If you talk to your sales engineer or contact support they can give you the run down on the possible interactions between sas and sata on the same filer; I was warned about performance issues but I've not had a problem even in takeover with 2 sas stacks and a sata stack all being pushed pretty hard.