Side-by-side specifications of the Synology DS1813+ and DS1815+, from official datasheets. Differences are highlighted.
| DS1813+ | DS1815+ | |
| CPU | dual-core CPU | Intel Atom C2538 |
| Cores / threads | 2 cores / unknown threads | 4 cores / 4 threads |
| RAM (base) | 2 GB | 2 GB DDR3 |
| RAM (max) | 4 GB | 6 GB |
| Drive bays | 8 | 8 |
| Expandable to | 10 (2 DX513 units) | 10 (DX513; 18 total) |
| M.2 slots | 0 | 0 |
| Network | 4 x Gigabit | 4x Gigabit Ethernet |
| 10GbE | no | no |
| Max raw capacity | 72 TB | 48 TB internal; 108 TB with DX513 expansion |
| Hot-swap | yes | yes |
| Form factor | tower | Tower |
| Released | 2013 | 2014 |
| Power consumption | 75.19 W / 34.12 W | — |
| DSM at launch | — | — |
Pick the DS1815+ if you want the newer Atom C2538 CPU, more RAM headroom, and better scaling: it supports up to 6 GB RAM versus 4 GB on the DS1813+, keeps 8 bays, and can expand to 17 bays with the DX513. Neither model has built-in 10GbE or M.2, so those aren’t deciding factors here.