Side-by-side specifications of the Synology DS1517 and DS1520+, from official datasheets. Differences are highlighted.
| DS1517 | DS1520+ | |
| CPU | Annapurna Labs Alpine AL-314 1.7GHz | Intel Celeron J4125 |
| Cores / threads | 4 cores / 4 threads | 4 cores / 4 threads |
| RAM (base) | 2 GB DDR3L | 8 GB DDR4 non-ECC |
| RAM (max) | 2 GB | 8 GB |
| Drive bays | 5 | 5 |
| Expandable to | 10 (2× DX517) | 15 total (2 DX517) |
| M.2 slots | 0 | 2 NVMe M.2 2280 |
| Network | 4× 1GbE RJ-45 | 4 x 1GbE RJ-45 |
| 10GbE | no | no |
| Max raw capacity | 75 TB | 80 TB internal raw; 108 TB maximum single volume |
| Hot-swap | yes | yes |
| Form factor | Desktop | Desktop |
| Released | 2017 | 2020 |
| Power consumption | 39.5 W / null | 52.06 W / 16.07 W |
| DSM at launch | — | 7.0 |