Side-by-side specifications of the Synology RS3626xs and RS4021xs+, from official datasheets. Differences are highlighted.
| RS3626xs | RS4021xs+ | |
| CPU | Intel Xeon D-1726 | Intel Xeon D-1541 |
| Cores / threads | 6 cores / 12 threads | 8 cores / 16 threads |
| RAM (base) | 8 GB DDR4 ECC UDIMM | 16 GB DDR4 ECC UDIMM |
| RAM (max) | 48 GB | 64 GB |
| Drive bays | 12 | 16 |
| Expandable to | 36 | 40 (with 2× RX1217/RX1217RP) |
| M.2 slots | 0 built-in; optional via adapter card | Optional via PCIe adapter cards |
| Network | 2× 10GbE RJ-45, 1× out-of-band management LAN | 4× 1GbE RJ-45; 2× 10GbE RJ-45 |
| 10GbE | yes | yes |
| Max raw capacity | 36 drives | 1 PB single volume |
| Hot-swap | yes | yes |
| Form factor | 2U rackmount | 3U rackmount |
| Released | 2026 | 2021 |
| Power consumption | 147.79 W / 75.73 W | 145.79 W / 62.68 W |
| DSM at launch | — | — |