Side-by-side specifications of the Synology DS1517 and DS1517+, from official datasheets. Differences are highlighted.
| DS1517 | DS1517+ | |
| CPU | Annapurna Labs AL-314 | Intel Atom C2538 |
| Cores / threads | 4 | 4c/4t |
| RAM (base) | 2 GB | 2 GB |
| RAM (max) | 16 GB | 16 GB |
| Drive bays | 5 | 5 |
| Expandable to | 15 | 10 |
| M.2 slots | 2 | 2 |
| Network | 4x1GbE | 4x1GbE |
| 10GbE | optional | optional |
| Max raw capacity | 75 TB | 108 TB |
| Hot-swap | yes | yes |
| Form factor | desktop | desktop |
| Released | 2016 | 2017 |
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.