Side-by-side specifications of the Synology DS119j and DS120j, from official datasheets. Differences are highlighted.
| DS119j | DS120j | |
| CPU | Marvell Armada 3700 88F3720, 800 MHz | Marvell Armada 3700 88F3720 |
| Cores / threads | 2 cores / 2 threads | 2 cores / 2 threads |
| RAM (base) | 256 MB DDR3L non-ECC | 512 MB DDR3L |
| RAM (max) | 256 MB | 512 MB |
| Drive bays | 1 | 1 |
| Expandable to | 0 | 0 |
| M.2 slots | 0 | 0 |
| Network | 1 x 1GbE RJ-45 | 1 x 1GbE RJ-45 |
| 10GbE | no | no |
| Max raw capacity | 12 TB raw; 108 TB maximum single volume | 16 TB |
| Hot-swap | no | no |
| Form factor | Desktop | Desktop |
| Released | 2018 | 2020 |
| Power consumption | 10.04 W / 5.01 W | — |
| DSM at launch | — | — |
Pick the DS120J if you want a newer 2-bay unit with a faster CPU and better upgrade headroom: it has 512 MB RAM versus 256 MB on the DS119j, and one extra bay for RAID/expansion flexibility. Neither model has 10GbE or M.2, so those aren’t deciding factors here. The DS119j is only worth it if you’re getting it significantly cheaper and can live with a single bay and lower RAM ceiling.