Got ya. Yeah, prod and DR and for sure "uneven" so that would explain the 100% usage you're seeing.
Your NetApp Partner can run sizing to see what would be a proper DR target options for you. I don't think a headswap would be the thing to do honestly and i'm pretty sure you can't swap a 25xx to a 27xx either.
You can probably re-use the 2554's chassis and disks as a DS4246 or even put in a IOM12. But it's still just a pool of SATA. And if you're running AFF in prod, there is no real comparison. You'd probably have to work in Flashpool to use with the SATA (if you don't have it already in the 2554). Still have that 8020 laying around? That might make a decent DR target with the correct disks.
