Side-by-side specifications of the Synology DS409 and DS409+, from official datasheets. Differences are highlighted.
| DS409 | DS409+ | |
| CPU | 1.2GHz | Marvell Orion 6281 |
| Cores / threads | — | 1/1 |
| RAM (base) | 256MB | 256 MB |
| RAM (max) | — | 512 MB |
| Drive bays | 4 | 4 |
| Expandable to | — | 0 |
| M.2 slots | 0 | 0 |
| Network | 1x Gigabit | 2x 1GbE |
| 10GbE | no | no |
| Max raw capacity | 4TB | 8 TB |
| Hot-swap | yes | yes |
| Form factor | desktop | desktop |
| Released | 2009 | 2009 |
Choose the DS409+ if you want the stronger platform: it has a faster CPU and more RAM headroom than the DS409. Both are 4-bay NAS units with no expansion, and neither has 10GbE or M.2 support. If you only need basic file backup/media storage, the DS409 is enough; if you expect heavier multitasking or more users, get the DS409+.