Side-by-side specifications of the Synology DS409slim and DS420+, from official datasheets. Differences are highlighted.
| DS409slim | DS420+ | |
| CPU | 1.2GHz | Intel Celeron J4025 |
| Cores / threads | — | 2 cores, 2 threads |
| RAM (base) | 128MB | 2 GB DDR4 |
| RAM (max) | 128MB | 6 GB |
| Drive bays | 4 | 4 |
| Expandable to | 0 | 0 |
| M.2 slots | 0 | 2 |
| Network | 1x Gigabit | 2x GbE RJ-45 |
| 10GbE | no | no |
| Max raw capacity | 3TB | 64 TB |
| Hot-swap | yes | yes |
| Form factor | 2.5" NAS | desktop |
| Released | 2010 | 2020 |