Side-by-side specifications of the Synology DS1517 and DS1517+, from official datasheets. Differences are highlighted.
| DS1517 | DS1517+ | |
| CPU | Annapurna Labs Alpine AL-314 1.7GHz | Intel Atom C2538 2.4GHz |
| Cores / threads | 4 cores / 4 threads | 4 cores / 4 threads |
| RAM (base) | 2 GB DDR3L | 2 GB DDR3 SO-DIMM |
| RAM (max) | 2 GB | 16 GB |
| Drive bays | 5 | 5 |
| Expandable to | 10 (2× DX517) | 10 (2×DX517) |
| M.2 slots | 0 | 2 via M2D17 adapter |
| Network | 4× 1GbE RJ-45 | 4×1GbE RJ-45 |
| 10GbE | no | optional |
| Max raw capacity | 75 TB | 108 TB |
| Hot-swap | yes | yes |
| Form factor | Desktop | Desktop |
| Released | 2017 | 2017 |
| Power consumption | 39.5 W / null | — |
| DSM at launch | — | — |
Choose the DS1517+ if you want the stronger Intel CPU, higher RAM ceiling, and built-in NVMe M.2 slots for caching; those are the most practical upgrades for SMB use. The DS1517 is the lower-tier Atom model with less headroom, while both are 5-bay units with expansion support and can be upgraded to 10GbE via add-in card. If you care about performance now or future growth, the DS1517+ is the safer buy.