Side-by-side specifications of the Synology RS217 and RS407, from official datasheets. Differences are highlighted.
| RS217 | RS407 | |
| CPU | Marvell ARMADA 385 88F6820 1.33GHz | 500 MHz |
| Cores / threads | 2 cores / 2 threads | — |
| RAM (base) | 512 MB DDR3 | 128 MB |
| RAM (max) | 512 MB | — |
| Drive bays | 2 | 4 |
| Expandable to | 0 | 0 |
| M.2 slots | 0 | 0 |
| Network | 2x 1GbE RJ-45 | 1× Gigabit |
| 10GbE | no | no |
| Max raw capacity | 28 TB | 4 TB |
| Hot-swap | yes | yes |
| Form factor | 1U rackmount | 1U rackmount |
| Released | 2016 | — |
| Power consumption | — | 60 W / 21 W |
| DSM at launch | — | — |
Choose the RS407 if you need more headroom: it has the stronger CPU, higher RAM ceiling, four bays instead of two, and no expansion path on the RS217 makes capacity much more limited. Neither model has 10GbE or M.2, so the real deciding factors are CPU/RAM and bay count; the RS217 is only the pick if you want the cheapest, simplest 2-bay unit.