Side-by-side specifications of the Synology DS209 and DS209+, from official datasheets. Differences are highlighted.
| DS209 | DS209+ | |
| CPU | 1.2 GHz | 800 MHz |
| Cores / threads | 1 core / 1 thread | 1 core / 1 thread |
| RAM (base) | 256 MB | 512 MB |
| RAM (max) | 256 MB | 512 MB |
| Drive bays | 2 | 2 |
| Expandable to | 0 | 0 |
| M.2 slots | 0 | 0 |
| Network | 1x Gigabit | 1× Gigabit |
| 10GbE | no | no |
| Max raw capacity | 4 TB | 2 TB |
| Hot-swap | no | no |
| Form factor | desktop | Desktop |
| Released | 2009 | 2008 |
| Power consumption | 25 W / unknown | 32.4 W / 18 W |
| DSM at launch | 2.2 | 2.0 |
Choose the DS209+ if you want the stronger CPU and higher RAM ceiling; those are the only meaningful performance advantages. Both are 2-bay units with no expansion beyond the two drives, and neither has 10GbE or M.2. For basic file storage and backups, the DS209 is enough; for heavier multitasking or slower-latency services, the DS209+ is the better pick.