Side-by-side specifications of the Synology FS3420 and FS6400, from official datasheets. Differences are highlighted.
| FS3420 | FS6400 | |
| CPU | Intel Xeon D-1739 | 2 × Intel Xeon Silver 4110, 2.1/3.0 GHz |
| Cores / threads | 8 cores / 16 threads | 16 cores / 32 threads total |
| RAM (base) | 32 GB DDR4 ECC RDIMM | 32 GB DDR4 ECC RDIMM |
| RAM (max) | 192 GB | 512 GB |
| Drive bays | 24 × 2.5-inch SATA SSD | 24 × 2.5-inch SAS HDD/SSD or SATA SSD |
| Expandable to | 0 | 48 with 2 × RX1222sas; 72 with 2 × FX2421 |
| M.2 slots | 0 | 0 |
| Network | 2 × 10GbE RJ-45 | 2 × 1GbE RJ-45; 2 × 10GbE RJ-45 |
| 10GbE | yes | yes |
| Max raw capacity | 1 PB | 184.32 TB raw internal |
| Hot-swap | yes | yes |
| Form factor | 2U rackmount | 2U rackmount |
| Released | 2026 | 2018 |
| Power consumption | 122.0 W / unknown | 288.49 W / 145.8 W |
| DSM at launch | — | — |