Side-by-side specifications of the Synology DS1522+ and DS1621+, from official datasheets. Differences are highlighted.
| DS1522+ | DS1621+ | |
| CPU | AMD Ryzen R1600 | AMD Ryzen V1500B |
| Cores / threads | 2/4 | 4 |
| RAM (base) | 8 GB | 4 GB |
| RAM (max) | 32 GB | 32 GB |
| Drive bays | 5 | 6 |
| Expandable to | 10 | 16 |
| M.2 slots | 2 | 2 |
| Network | 4x 1GbE | 4x 1GbE RJ-45 |
| 10GbE | optional | optional |
| Max raw capacity | 15 drives | 256 TB |
| Hot-swap | yes | yes |
| Form factor | desktop | desktop |
| Released | 2022 | 2020 |
Choose the DS1621+ if you want the stronger platform: it has the better CPU, supports up to 32 GB RAM, has 6 bays instead of 5, and expands farther; it also offers 10GbE expansion but no built-in 10GbE, and it uses M.2 slots for SSD cache. Choose the DS1522+ if you want the newer, simpler 5-bay unit with built-in 2.5GbE and M.2 cache slots, but it has a weaker CPU and a lower RAM ceiling than the DS1621+.