Side-by-side specifications of the Synology RS409+ and RS411, from official datasheets. Differences are highlighted.
| RS409+ | RS411 | |
| CPU | — | 1.6 GHz |
| Cores / threads | — | 1/1 |
| RAM (base) | — | 512 MB |
| RAM (max) | — | 512 MB |
| Drive bays | 4 | 4 |
| Expandable to | 4 via RX4 | 0 |
| M.2 slots | 0 | 0 |
| Network | 2 x Gigabit | 2 x Gigabit Ethernet |
| 10GbE | no | no |
| Max raw capacity | 8 HDDs | 16 TB |
| Hot-swap | yes | yes |
| Form factor | 1U rackmount | 1U rackmount |
| Released | 2009 | 2010 |
| Power consumption | 28 W / 9.5 W | 53 W / unknown |
| DSM at launch | 2.1 | 3.0 |
Choose the RS411 if you want the newer, clearly more capable unit: it has a faster CPU, much higher RAM ceiling, and supports expansion to more bays. Neither model is a modern 10GbE or M.2 box, so if those are requirements, you should skip both and look at a newer Synology.