Side-by-side specifications of the Synology DS1511+ and DS1515, from official datasheets. Differences are highlighted.
| DS1511+ | DS1515 | |
| CPU | 1.8GHz dual-core | quad-core CPU |
| Cores / threads | 2 | 4 |
| RAM (base) | 1GB | 2GB |
| RAM (max) | 3GB | 6GB |
| Drive bays | 5 | 5 |
| Expandable to | 15 | 15 |
| M.2 slots | 0 | 0 |
| Network | 2x Gigabit | 4x 1GbE |
| 10GbE | no | no |
| Max raw capacity | 15TB | 40TB |
| Hot-swap | yes | yes |
| Form factor | Desktop | desktop |
| Released | 2011 | 2015 |