Side-by-side specifications of the Synology DS109 and DS109j, from official datasheets. Differences are highlighted.
| DS109 | DS109j | |
| CPU | 1.2 GHz | — |
| Cores / threads | 1 core / 1 thread | — |
| RAM (base) | 128 MB | — |
| RAM (max) | — | — |
| Drive bays | 1 | 1 |
| Expandable to | 0 | 0 |
| M.2 slots | 0 | 0 |
| Network | 1× Gigabit Ethernet | 1× Gigabit Ethernet |
| 10GbE | no | no |
| Max raw capacity | 2 TB | — |
| Hot-swap | no | no |
| Form factor | Desktop | Desktop |
| Released | 2009 | 2009 |
| Power consumption | 19 W / 9 W | 26 W / 10 W |
| DSM at launch | 2.2 | 2.1 |
Choose the DS109: it has a faster CPU and supports more RAM, while both are single-bay units with no expansion, 10GbE, or M.2 support. The DS109j is the lower-cost option for basic file sharing, but its weaker CPU and lower RAM ceiling make it less suitable for heavier workloads.