Side-by-side specifications of the Synology FS3400 and FS3420, from official datasheets. Differences are highlighted.
| FS3400 | FS3420 | |
| CPU | Intel Xeon D-1541 2.1 GHz | Intel Xeon D-1739 |
| Cores / threads | 8 cores / 16 threads | 8 cores / 16 threads |
| RAM (base) | 16 GB DDR4 ECC RDIMM | 32 GB DDR4 ECC RDIMM |
| RAM (max) | 128 GB | 192 GB |
| Drive bays | 24 | 24 × 2.5-inch SATA SSD |
| Expandable to | 72 | 0 |
| M.2 slots | 0 | 0 |
| Network | 4 x 1GbE RJ-45, 2 x 10GbE RJ-45 | 2 × 10GbE RJ-45 |
| 10GbE | yes | yes |
| Max raw capacity | 184.32 TB | 1 PB |
| Hot-swap | yes | yes |
| Form factor | 2U rackmount | 2U rackmount |
| Released | 2022 | 2026 |
| Power consumption | 313.84 W / 125.77 W | 122.0 W / unknown |
| DSM at launch | — | — |