Side-by-side specifications of the Synology DS1515+ and DS1520+, from official datasheets. Differences are highlighted.
| DS1515+ | DS1520+ | |
| CPU | Intel Atom C2538 | Intel Celeron J4125 |
| Cores / threads | 4 cores / 4 threads | 4 cores / 4 threads |
| RAM (base) | 2 GB DDR3 | 8 GB DDR4 non-ECC |
| RAM (max) | 6 GB | 8 GB |
| Drive bays | 5 | 5 |
| Expandable to | 10 (with DX513) | 15 total (2 DX517) |
| M.2 slots | 0 | 2 NVMe M.2 2280 |
| Network | 4 x Gigabit | 4 x 1GbE RJ-45 |
| 10GbE | no | no |
| Max raw capacity | 30 TB internal; 90 TB with DX513 expansion | 80 TB internal raw; 108 TB maximum single volume |
| Hot-swap | yes | yes |
| Form factor | Desktop | Desktop |
| Released | 2015 | 2020 |
| Power consumption | 72.5 W / 18.4 W | 52.06 W / 16.07 W |
| DSM at launch | — | 7.0 |