Side-by-side specifications of the Synology DS409+ and DS409slim, from official datasheets. Differences are highlighted.
| DS409+ | DS409slim | |
| CPU | Marvell Orion 6281 | 1.2GHz |
| Cores / threads | 1/1 | — |
| RAM (base) | 256 MB | 128MB |
| RAM (max) | 512 MB | 128MB |
| Drive bays | 4 | 4 |
| Expandable to | 0 | 0 |
| M.2 slots | 0 | 0 |
| Network | 2x 1GbE | 1x Gigabit |
| 10GbE | no | no |
| Max raw capacity | 8 TB | 3TB |
| Hot-swap | yes | yes |
| Form factor | desktop | 2.5" NAS |
| Released | 2009 | 2010 |
Pick the DS409+ if you want a faster Intel CPU, much higher RAM ceiling, and 4 full-size drive bays; it’s the better choice for most home/SMB use. The DS409slim is the compact 2.5-inch model with far less expandability and lower-end hardware, so it’s only worth it if size and low-power use matter most. Neither unit has 10GbE or M.2.