I have a late 2012 27-inch iMac (Slim unibody iMac without Retina Display) that was BTO'd with a 1TB Fusion Drive. 1TB HDD died within the last 12 months so I have been running on the 128GB Blade SSD SATA I am choosing between these two upgrades Option 1 Dual 1TB SSD through MaxUpgrades that allows for two 2.5" 1TB SSDs to run on RAID 0. Throughput would be 1,000MB/s. Option 2 Install a 12TB Seagate BarraCuda HDD with the original 128GB Blade SSD SATA and make a new Fusion Drive. I do not see myself buying a new iMac until Q1 2023. I will have a 12TB Time Machine backup.