Side-by-side specifications of the Synology DS1517 and DS1621+, from official datasheets. Differences are highlighted.
| DS1517 | DS1621+ | |
| CPU | Annapurna Labs Alpine AL-314 1.7GHz | AMD Ryzen V1500B, 2.2 GHz |
| Cores / threads | 4 cores / 4 threads | 4 cores / 8 threads |
| RAM (base) | 2 GB DDR3L | 4 GB DDR4 ECC SODIMM |
| RAM (max) | 2 GB | 32 GB (16 GB x 2) |
| Drive bays | 5 | 6 |
| Expandable to | 10 (2× DX517) | 16 total with 2 DX517 units |
| M.2 slots | 0 | 2 x M.2 2280 NVMe |
| Network | 4× 1GbE RJ-45 | 4 x 1GbE RJ-45 |
| 10GbE | no | optional |
| Max raw capacity | 75 TB | 256 TB raw with 2 DX517 units |
| Hot-swap | yes | yes |
| Form factor | Desktop | desktop |
| Released | 2017 | 2020 |
| Power consumption | 39.5 W / null | 51.22 W / 25.27 W |
| DSM at launch | — | — |