Side-by-side specifications of the Synology DS1515 and DS1515+, from official datasheets. Differences are highlighted.
| DS1515 | DS1515+ | |
| CPU | Annapurna Labs Alpine AL-514 | Intel Atom C2538 |
| Cores / threads | 4 cores / 4 threads | 4 cores / 4 threads |
| RAM (base) | 2 GB | 2 GB DDR3 |
| RAM (max) | 2 GB | 6 GB |
| Drive bays | 5 | 5 |
| Expandable to | 15 | 10 (with DX513) |
| M.2 slots | 0 | 0 |
| Network | 4 x 1GbE | 4 x Gigabit |
| 10GbE | no | no |
| Max raw capacity | 40 TB | 30 TB internal; 90 TB with DX513 expansion |
| Hot-swap | yes | yes |
| Form factor | Desktop | Desktop |
| Released | 2015 | 2015 |
| Power consumption | — | 72.5 W / 18.4 W |
| DSM at launch | — | — |
Choose the DS1515+ if you want materially better performance: it uses a much faster Intel C2538 CPU and supports a higher RAM ceiling than the DS1515’s Annapurna Labs chip. Both are 5-bay units with the same 2× eSATA expansion support, and neither has built-in 10GbE or M.2; between them, the + model is the decisive pick for SMB use.