Side-by-side specifications of the Synology RS409 and RS409+, from official datasheets. Differences are highlighted.
| RS409 | RS409+ | |
| CPU | 1.2GHz | — |
| Cores / threads | — | — |
| RAM (base) | 256MB | — |
| RAM (max) | — | — |
| Drive bays | 4 | 4 |
| Expandable to | 4 | 4 via RX4 |
| M.2 slots | 0 | 0 |
| Network | 2x Gigabit | 2 x Gigabit |
| 10GbE | no | no |
| Max raw capacity | 3TB | 8 HDDs |
| Hot-swap | yes | yes |
| Form factor | 1U rackmount | 1U rackmount |
| Released | — | 2009 |
| Power consumption | 52.8 W / 23 W | 28 W / 9.5 W |
| DSM at launch | 2.1 | 2.1 |
Choose the RS409+ if you need more performance: it has a faster Intel Atom CPU and supports up to 2GB RAM, versus the RS409’s slower CPU and 1GB ceiling. Both are 4-bay units with no 10GbE, M.2 slots, or meaningful bay expansion, so those features do not distinguish them.