Side-by-side specifications of the Synology HD6500 and RS4021xs+, from official datasheets. Differences are highlighted.
| HD6500 | RS4021xs+ | |
| CPU | 2x Intel Xeon Silver 4210R | Intel Xeon D-1541 |
| Cores / threads | 20 cores / 40 threads | 8/16 |
| RAM (base) | 64 GB | 16 GB |
| RAM (max) | 512 GB | 64 GB |
| Drive bays | 60 | 16 |
| Expandable to | 300 | 40 |
| M.2 slots | 0 | via PCIe adapters |
| Network | 2x 1GbE + 2x 10GbE + 1x OOB | 4x 1GbE RJ-45, 2x 10GbE RJ-45 |
| 10GbE | yes | yes |
| Max raw capacity | 1 PB | 1 PB |
| Hot-swap | yes | yes |
| Form factor | 4U rackmount | 3U rackmount |
| Released | 2025 | 2025 |