Side-by-side specifications of the Synology HD6500 and RS4021xs+, from official datasheets. Differences are highlighted.
| HD6500 | RS4021xs+ | |
| CPU | 2× Intel Xeon Silver 4210R, 2.4/3.2 GHz | Intel Xeon D-1541 |
| Cores / threads | 20 cores / 40 threads total | 8 cores / 16 threads |
| RAM (base) | 64 GB DDR4 ECC RDIMM | 16 GB DDR4 ECC UDIMM |
| RAM (max) | 512 GB | 64 GB |
| Drive bays | 60 | 16 |
| Expandable to | 240 (up to 300 total) | 40 (with 2× RX1217/RX1217RP) |
| M.2 slots | 0 | Optional via PCIe adapter cards |
| Network | 2×1GbE + 2×10GbE + 1×out-of-band management | 4× 1GbE RJ-45; 2× 10GbE RJ-45 |
| 10GbE | yes | yes |
| Max raw capacity | 1 PB single volume / 300 drives | 1 PB single volume |
| Hot-swap | yes | yes |
| Form factor | 4U rackmount | 3U rackmount |
| Released | 2025 | 2021 |
| Power consumption | 1025.2 W / 418 W | 145.79 W / 62.68 W |
| DSM at launch | — | — |