Side-by-side specifications of the Synology DS209j and DS210+, from official datasheets. Differences are highlighted.
| DS209j | DS210+ | |
| CPU | 266MHz 32-bit with floating point | 1.06 GHz 64-bit |
| Cores / threads | 1/1 | — |
| RAM (base) | 64MB | DDR |
| RAM (max) | — | — |
| Drive bays | 2 | 2 |
| Expandable to | 0 | 0 |
| M.2 slots | 0 | 0 |
| Network | 1x Gigabit | 1GbE |
| 10GbE | no | no |
| Max raw capacity | 4TB (2x 2TB) | — |
| Hot-swap | no | — |
| Form factor | Desktop | desktop |
| Released | 2009 | 2010 |
| Power consumption | 15–36 W / unknown | 30 W / null |
| DSM at launch | 2.2 | 2.3 |
Choose the DS210+ if you want the clearly better box: it has a much faster CPU, far more RAM headroom, and support for 2 bays plus expansion. Neither the DS209j nor DS210+ has 10GbE or M.2; if those matter, you need a much newer model.