I am upgrading my Synology from a 5-bay 1517+ to a new 8-bay 1821+. I decided to go with Seagate IronWolf Pro 4TB drives since they are so cheap now. I have a little over 20 terabytes of space on each, but I was able to configure the new one with SHR-2 so there can be two drive failures without data loss. I also set up the SSD Cache with two 500GB 970 EVO Plus drives. Finally, I upgraded the standard 4GB of memory to 32GB. In addition to storage, I plan to use this for VMs, Docker containers and maybe a new place for my Plex server.