Side-by-side specifications of the Synology DS1815+ and DS1817, from official datasheets. Differences are highlighted.
| DS1815+ | DS1817 | |
| CPU | Intel Atom C2538 | Intel Atom C2538 1.7 GHz |
| Cores / threads | 4 cores / 4 threads | quad-core/4 threads |
| RAM (base) | 2 GB DDR3 | 4 GB |
| RAM (max) | 6 GB | 8 GB |
| Drive bays | 8 | 8 |
| Expandable to | 10 (DX513; 18 total) | 10 |
| M.2 slots | 0 | 0 |
| Network | 4x Gigabit Ethernet | 2 x 1GbE RJ-45, 2 x 10GBASE-T RJ-45 |
| 10GbE | no | yes |
| Max raw capacity | 48 TB internal; 108 TB with DX513 expansion | 180 TB |
| Hot-swap | yes | yes |
| Form factor | Tower | desktop |
| Released | 2014 | 2017 |
| Power consumption | — | — |
| DSM at launch | — | — |
Choose the DS1817 if you want the better all-around platform: it has the faster Intel Atom C2538 CPU, supports up to 8 GB RAM, and can expand with the DX517 to 17 bays total. It also has an optional 10GbE NIC slot, while the DS1815+ is the older Atom C2538-based model with lower practical headroom, 6 GB RAM max, and the same 8-bay/17-bay-with-expansion layout but no M.2 support on either unit. If you don’t need 10GbE and want to save money, the DS1815+ is fine, but the DS1817 is the better buy for longevity and upgrades.